Air conditioning with recovery wheel, passive dehumidification wheel, cooling coil, and secondary direct-expansion circuit

ABSTRACT

Air conditioning units, systems, and methods that control temperature and humidity within a space in a building, for example, using a recovery wheel, a desiccant-based or passive dehumidification wheel, a primary cooling coil; and a secondary direct-expansion refrigeration circuit that includes a secondary circuit compressor, a secondary circuit evaporator coil, and a secondary circuit condenser coil. In various embodiments, the system forms a supply airstream that passes outdoor air first through the recovery wheel, then through the primary cooling coil, then through the secondary circuit evaporator coil, then through the dehumidification wheel, and then to the space. Further, in many embodiments, the system forms an exhaust airstream that passes return air from the space first through the secondary circuit condenser coil, then through the dehumidification wheel, and then through the recovery wheel. In some embodiments, various quantities of heat and moisture are transferred between the two airstreams.

RELATED PATENT APPLICATIONS

This U.S. non-provisional patent application claims priority to U.S.Provisional Patent Application Ser. No. 62/347,517, filed on Jun. 8,2016, and has the same title, inventor, and assignee. The contents ofthe priority provisional patent application are incorporated herein byreference.

FIELD OF THE INVENTION

Various embodiments of this invention relate to air conditioning units,systems, and methods that control temperature and humidity, for example,within a space within a building. Many embodiments transfer heat,moisture, or both, from outdoor air in a supply airstream to an exhaustairstream. Certain embodiments relate to air conditioning units,systems, and methods that include or use a recovery wheel, a passivedehumidification wheel, and a cooling coil.

BACKGROUND OF THE INVENTION

Heating, ventilating, and air-conditioning (HVAC) systems have been usedto maintain desirable temperatures and humidity levels within buildings,and buildings have been constructed with ventilation systems, includingHVAC systems, to provide comfortable and safe environments for occupantsto live and work. To maintain fresh air within buildings and to reducethe level of indoor air contaminants, in many applications, at least aportion of the air handled by ventilation or HVAC systems has been takenfrom outdoors, while a portion of the indoor air handled by HVAC systemshas been exhausted, for example, to outside the building.

In many situations, outside air introduced to the building to replaceexhaust air must be cooled or heated before being introduced to thebuilding to provide temperatures within desired parameters, and oftenmust be dehumidified or humidified to keep humidity levels withindesired ranges. But adding or removing heat or humidity (moisture)typically involves the expenditure of energy. To reduce the energyrequired to condition the outside air, recovery wheels anddesiccant-based dehumidification wheels, including passivedehumidification wheels, have been used to transfer heat, moisture, orboth, between exhaust air and incoming outside air. Examples of theprior art in these areas are described in U.S. Pat. Nos. 4,769,053 and6,199,388, and U.S. patent application publication number 2004/0000152,all having at least one inventor in common with the subject matter ofthis document, and all of which are incorporated herein by reference intheir entirety. Certain terms, however, may be used differently in thedocuments that are incorporated by reference, and if any conflictsexist, this document shall govern herein. These prior art documents alsodescribe many of the potential needs and benefits of such systems andthe use of recovery wheels.

In addition, cooling coils have been used to cool and dehumidify outdoorair that is introduced to a building, including cooling coils that arecooled with chilled water that has been cooled by one or more chillers.Furthermore, U.S. Pat. No. 6,199,388 describes systems and methods forcontrolling temperature and humidity that include a recovery wheel, apassive dehumidification wheel, and a cooling coil, wherein the systemforms a supply airstream that passes outdoor air first through therecovery wheel, then through the cooling coil, then through thedesiccant-based passive dehumidification wheel, and then to the space,and the system forms an exhaust airstream that passes return air fromthe space first through the desiccant-based passive dehumidificationwheel, and then through the recovery wheel. Examples of prior artsystems are shown in FIGS. 2 and 4.

Further, chilled beams have been used to cool spaces within buildings.Patent application publication No. 20130199772 describes active andpassive chilled beams and is also incorporated herein by reference.Active chilled beams have been used wherein outdoor air is cooled anddehumidified to become supply air, which is delivered to the chilledbeams where the supply air is released into the space through slots ornozzles in a manner that causes induction of room air across a coolingcoil positioned within the chilled beam, thereby substantiallyincreasing cooling capacity delivered to the space. Lower levels ofhumidity in the supply air would be beneficial in some such situationsbecause the chilled beams themselves do not remove humidity from theroom air and the supply air may be the only source of dehumidification.Further still, in chilled beam applications, humidity levels in the roomair can limit the amount of cooling that can be provided through thechilled beams because the chilled beams cannot be cooled below the roomair dew point or else condensation will occur on the chilled beams whichwill drip on the occupants and other contents of the space. Avoidingsuch condensation is necessary or beneficial in many situations.

Still further, chillers that produce chilled water have been used as anefficient way to provide cooling and dehumidification, particularly forlarge buildings. In chilled water systems, however, the minimumtemperature that the air leaving the cooling coil can reach has beenlimited by how cold the chilled water can be produced using traditionalchiller performance limitations. As a result, the amount of humiditythat can be removed from the outdoor air, for example, is limited. Lowerlevels of humidity in the supply air, however, would be beneficial insome situations, for example, where chilled beams are used. In addition,supply air volume (i.e., flow rate) is often desired to be greater thanexhaust air volume to achieve proper building pressurization to preventinfiltration, but in prior art systems, particularly when the imbalancebetween supply air volume and exhaust air volume is sufficiently high,condensation has occurred within the exhaust airstream, for instance, onthe dehumidification wheel or between the dehumidification wheel and therecovery wheel. Avoiding such condensation would be beneficial, if notessential, in many situations. Moreover, in prior art systems, whensupply air was cooled in the cooling coil sufficiently to provide thedesired level of supply air humidity, supply air temperatures were oftencolder than desired. Warmer supply air temperatures would be beneficialin such situations. Needs and opportunities for improvement exist forpartially or fully providing one or more of these needs or potentialbenefits. Room for improvement exists over the prior art in these andvarious other areas that may be apparent to a person of ordinary skillin the art having studied this document.

SUMMARY OF PARTICULAR EMBODIMENTS OF THE INVENTION

This invention provides, among other things, various air conditioningunits, systems, and methods that control temperature and humidity, forinstance, within a space in a building. Various units and systems, forexample, include a recovery wheel, a (e.g., passive) dehumidificationwheel, a primary cooling coil, a secondary cooling coil, and a heatingcoil. Further, in various embodiments, a supply airstream passes outdoorair first through the recovery wheel, then through the primary coolingcoil, then through the secondary cooling coil, then through thedehumidification wheel, and then to the space. Still further, in manyembodiments, an exhaust airstream passes return air from the space firstthrough the heating coil, then through the dehumidification wheel, andthen through the recovery wheel.

Various embodiments provide, for example, as an object or benefit, thatthey partially or fully address or satisfy one or more of the needs,potential areas for benefit, or opportunities for improvement describedherein, or known in the art, as examples. For instance, variousembodiments provide for the removal of more moisture from air (e.g.,outdoor air), for instance, in comparison with certain alternatives,while removing much of the enthalpy differential between the outdoor andreturn airstreams using a recovery wheel, a (e.g., passive)dehumidification wheel, and a cooling coil that is cooled with chilledwater that has been cooled by one or more chillers. In some embodiments,for example, systems that primarily use chilled water for coolingprovide as much dehumidification as prior art 100 percentdirect-expansion systems while providing a higher energy efficiencyratio. Further, various embodiments allow for a greater supply airvolume (i.e., flow rate) than exhaust air volume to achieve properbuilding pressurization to prevent infiltration, without forming any oras much condensation within the exhaust airstream between thedehumidification wheel and the recovery wheel. Still further, manyembodiments provide for supply air temperatures that are not undesirablycold where such cold temperatures would otherwise have been necessary toobtain desired low levels of humidity, or else the inefficientexpenditure of energy to reheat supply air would have been required.

Even further, some embodiments provide dryer supply air than certainprior art alternatives (e.g., for compatibility with chilled beams),provide less risk of condensation or better cooling performance of thechilled beams (e.g., due to a lower dew point within the space), or acombination thereof. Certain embodiments provide, for example, asobjects or benefits, for instance, that they improve the performance ofactive chilled beam system designs. Different embodiments simplify thedesign and installation of chilled beam systems, reduce the installedcost of the technology, increase energy efficiency, or a combinationthereof, as examples. In addition, various other embodiments of theinvention are also described herein, and other benefits of certainembodiments may be apparent to a person of ordinary skill in the art.

Specific embodiments include various systems for controlling temperatureand humidity within a space in a building. In many embodiments, forexample, the system includes a recovery wheel, a desiccant-baseddehumidification wheel, a primary cooling coil, and a secondarydirect-expansion refrigeration circuit. Further, in various embodiments,the secondary direct-expansion refrigeration circuit includes asecondary circuit compressor, a secondary circuit evaporator coil, and asecondary circuit condenser coil. Still further, in a number ofembodiments, the system forms a supply airstream that passes outdoor airfirst through the recovery wheel, then through the primary cooling coil,then through the secondary circuit evaporator coil, then through thedesiccant-based dehumidification wheel, and then to the space. Evenfurther, in various embodiments, the system forms an exhaust airstreamthat passes return air from the space first through the secondarycircuit condenser coil, then through the desiccant-baseddehumidification wheel, and then through the recovery wheel.

In some embodiments, the recovery wheel is a total energy recovery wheelincludes a desiccant coating, the recovery wheel transfers sensible heatbetween the outdoor air of the supply airstream and the exhaustairstream, and the recovery wheel transfers moisture between the outdoorair of the supply airstream and the exhaust airstream. Further, in someembodiments, the desiccant-based dehumidification wheel is a passivedehumidification wheel. Further, in a number of embodiments, the systemincludes a supply fan located in the supply airstream that moves theoutdoor air first through the recovery wheel, then through the primarycooling coil, then through the secondary circuit evaporator coil, thenthrough the desiccant-based dehumidification wheel, and then to thespace. Still further, many embodiments include an exhaust fan located inthe exhaust airstream that moves the return air from the space firstthrough the secondary circuit condenser coil, then through thedesiccant-based dehumidification wheel, and then through the recoverywheel.

Some embodiments include a primary chiller that chills cooling waterthat passes through the primary cooling coil. Some embodiments, however,include a primary direct-expansion refrigeration circuit. In particularembodiments, the primary direct-expansion refrigeration circuit includesthe primary cooling coil, for example, which acts as a primaryevaporator when operating in a cooling mode. Further, in a number ofembodiments, the primary direct-expansion refrigeration circuit includesa primary condensing coil, which acts as a condenser when operating inthe cooling mode, and at least one primary compressor. Further still, insome embodiments, the exhaust airstream passes through the primarycondensing coil. Even further, in certain embodiments, the return air ofthe exhaust airstream passes first through the secondary circuitcondenser coil, then through the desiccant-based dehumidification wheel,then through the recovery wheel, and then through the primary condensingcoil. Even further still, in many embodiments, the primarydirect-expansion refrigeration circuit is a heat pump, for example, thatboth cools and heats the primary cooling coil depending on whethercooling or heating of the space is demanded.

Various embodiments include a partition between the supply airstream andthe exhaust airstream. Further, in a number of embodiments, the recoverywheel is located in a first opening in the partition, thedesiccant-based dehumidification wheel is located in a second opening inthe partition, and, at least adjacent to the partition, the supplyairstream and the exhaust airstream travel in substantially paralleldirections. Still further, in many embodiments, at least adjacent to thepartition, the supply airstream and the exhaust airstream travel insubstantially opposite directions. Further still, in variousembodiments, the system includes an enclosure, for example, thatcontains the recovery wheel, the desiccant-based dehumidification wheel,the primary cooling coil, the secondary circuit evaporator coil, thesecondary circuit condenser coil, at least part of the supply airstream,at least part of the exhaust airstream, and the partition.

Further, in particular embodiments, the system includes a geothermaldirect-expansion refrigeration circuit, for example, that uses ageothermal heat sink as a geothermal condenser in a cooling mode. Stillfurther, in some embodiments, the space includes multiple zones. Furtherstill, in certain embodiments, each of the multiple zones includes atleast one zone direct-expansion refrigeration circuit, for example, thatincludes a zone compressor, a zone indoor air coil, and a zone outdoorheat exchanger.

In some embodiments, the system includes a system controller, forexample, that is configured to perform one or more of certain acts, forinstance, under certain conditions or to control particular variables.Such acts, conditions, and variables can include, for example, operatingthe secondary circuit compressor whenever the system is operating in acooling mode, operating the secondary circuit compressor whenever thesystem is operating in a dehumidification mode, modulating cooling atthe primary cooling coil to control temperature of the space whenoperating in the cooling mode, modulating cooling at the primary coolingcoil to control absolute humidity level or dew point of the supplyairstream delivered to the space when operating in the dehumidificationmode, or a combination thereof. Further acts, conditions, and variablescan include, for example, modulating cooling at the primary cooling coilto control temperature of the supply airstream delivered to the spacewhen operating in the cooling mode, modulating cooling at the primarycooling coil to control absolute humidity level or dew point of thesupply airstream delivered to the space when operating in thedehumidification mode, or both. Still further additional acts,conditions and variables can include optimizing the rotational speed ofthe passive dehumidification wheel to provide more or less reheat energyto the supply airstream, and taking advantage of the increase in returnairstream temperature leaving the second stage condensing coil whilestill delivering the desired level of dehumidification.

Further, some embodiments include a system controller configured tomodulate rotational speed of the dehumidification wheel, for example,based on a measured temperature of the supply airstream delivered to thespace, to control the temperature of the supply airstream delivered tothe space, or both. Still further, some embodiments include a systemcontroller configured to modulate the secondary circuit compressor toadjust reheat capacity at the secondary condenser coil when operating ina cooling mode. Further still, in some embodiments, the system includesa system controller configured to operate the system in an economizermode in which cooling at the primary cooling coil is turned off and thesecondary circuit compressor is operated, for example, to dehumidify thesupply airstream with the secondary circuit evaporator coil and, in someembodiments, the desiccant-based dehumidification wheel. Even further,in some embodiments, the system includes a system controller configuredto operate the system in a part-load or recirculation mode in whichcooling at the primary cooling coil is modulated down or off and coolingat the secondary cooling coil is modulated to dehumidify the supplyairstream, for example, using the desiccant-based dehumidificationwheel.

Other specific embodiments include various methods, for example, forcontrolling temperature and humidity within a space in a building. Insome embodiments, the method includes simultaneous acts, for example, ofoperating a secondary circuit compressor, passing outdoor throughparticular equipment, and passing return air through certain equipment,for example, in a particular order. In many embodiments, the secondarycircuit compressor is part of a secondary direct-expansion refrigerationcircuit that includes the secondary circuit compressor, a secondarycircuit evaporator coil, and a secondary circuit condenser coil.Further, various methods include passing outdoor air first through arecovery wheel, then through a primary cooling coil, then through thesecondary circuit evaporator coil, then through a (e.g., passive)dehumidification wheel, and then to the space. Still further, variousmethods include passing return air from the space first through thesecondary circuit condenser coil, then through the (e.g., passive)dehumidification wheel, and then through the recovery wheel.

In some embodiments, the method further includes transferring moisturebetween the outdoor air and the return air with a desiccant coating onthe recovery wheel. Further, in some embodiments, the method includesmodulating the secondary circuit compressor, for example, to adjustreheat capacity at the secondary condenser coil, for instance, whenoperating in a dehumidification mode. Still further, in someembodiments, the method includes condensing moisture out of the outdoorair with the secondary circuit evaporator coil, transferring sensibleheat to the return air with the secondary circuit condenser coil, orboth. Further still, in some embodiments, the method includes operatinga primary chiller that chills cooling water, and passing the coolingwater through the primary cooling coil. On the other hand, someembodiments include operating a primary direct expansion refrigerationcircuit, for example, that cools the primary cooling coil and thatrejects heat through a primary condenser coil. Even further, certainembodiments include passing the return air from the space first throughthe secondary circuit condenser coil, then through the (e.g., passive)dehumidification wheel, then through the recovery wheel, and thenthrough the primary condenser coil.

Still other specific embodiments include methods (e.g., of controllingtemperature and humidity within a space in a building) that include(e.g., simultaneous) acts of transferring various quantities of head andmoisture at particular locations within a system and delivering a supplyairstream to the space. Various embodiments, for example, includetransferring a first quantity of heat from outdoor air entering a supplyairstream to an exhaust airstream. Further, a number of embodimentsinclude cooling the supply airstream downstream of the transferring ofthe first quantity of heat, for example, including condensing a secondquantity of moisture from the supply airstream. Still further, variousembodiments include transferring a third quantity of heat from thesupply airstream to return air entering the exhaust airstream. Furtherstill, in many embodiments, the transferring of the third quantity ofheat from the supply airstream takes place in the supply airstreamdownstream of the cooling of the supply airstream. Even further, invarious embodiments, the transferring of the third quantity of heat fromthe supply airstream includes condensing a fourth quantity of moisturefrom the supply airstream.

In a number of embodiments, the transferring of the third quantity ofheat from the supply airstream to the return air entering the exhaustairstream is performed using a secondary direct-expansion refrigerationcircuit. Further, in various embodiments, the secondary direct-expansionrefrigeration circuit includes a secondary circuit compressor, asecondary circuit evaporator coil located in the supply airstream, and asecondary circuit condenser coil located in the exhaust airstream. Stillfurther, many embodiments include transferring a fifth quantity ofmoisture from the supply airstream to the exhaust airstream. Furtherstill, in various embodiments, the transferring of the fifth quantity ofmoisture from the supply airstream to the exhaust airstream takes placein the supply airstream downstream of the transferring of the thirdquantity of heat from the supply airstream to the return air enteringthe exhaust airstream. Even further, in many embodiments, thetransferring of the fifth quantity of moisture from the supply airstreamto the exhaust airstream takes place in the exhaust airstream downstreamof the transferring of the third quantity of heat from the supplyairstream to return air entering the exhaust airstream.

Even further still, many embodiments include, in conjunction with thetransferring of the fifth quantity of moisture from the supply airstreamto the exhaust airstream, transferring a sixth quantity of sensible heatfrom the exhaust airstream to the supply airstream. Moreover, in anumber of embodiments, the transferring of the sixth quantity ofsensible heat from the exhaust airstream to the supply airstream takesplace in the supply airstream downstream of the transferring of thethird quantity of heat from the supply airstream to the return airentering the exhaust airstream. In addition, in many embodiments, thetransferring of the sixth quantity of sensible heat from the exhaustairstream to the supply airstream takes place in the exhaust airstreamdownstream of the transferring of the third quantity of heat from thesupply airstream to the return air entering the exhaust airstream.Furthermore, various embodiments include delivering the supply airstreamto the space downstream of the transferring of the sixth quantity ofsensible heat from the exhaust airstream to the supply airstream.Additionally, in a number of embodiments, the delivering of the supplyairstream to the space takes place in the supply airstream downstream ofthe transferring of the fifth quantity of moisture from the supplyairstream to the exhaust airstream. Meanwhile, in various embodiments,the transferring of the first quantity of heat from the outdoor airentering the supply airstream to the exhaust airstream takes place inthe exhaust airstream downstream of the transferring of the fifthquantity of moisture from the supply airstream to the exhaust airstream.

In some embodiments, the first quantity of heat includes both sensibleand latent heat. Further, in particular embodiments, the act oftransferring the first quantity of heat from outdoor air entering thesupply airstream to the exhaust airstream further includes transferringa seventh quantity of moisture from the outdoor air entering the supplyairstream to the exhaust airstream. Still further, in certainembodiments, the transferring of the seventh quantity of moisture fromthe outdoor air entering the supply airstream to the exhaust airstreamtakes place in the exhaust airstream downstream of the transferring ofthe fifth quantity of moisture from the supply airstream to the exhaustairstream. Even further, in some embodiments, the cooling of the supplyairstream downstream of the transferring of the first quantity of heatincludes removing an eighth quantity of heat from the supply airstreamand rejecting the eighth quantity of heat to the exhaust airstreamdownstream, for example, of the transferring of the first quantity ofheat to the exhaust airstream. Even further still, in some embodiments,the cooling of the supply airstream downstream of the transferring ofthe first quantity of heat comprises operating a primarydirect-expansion refrigeration circuit, for example, that includes atleast one primary circuit compressor, a primary circuit evaporator coillocated in the supply airstream, and a primary circuit condenser coillocated in the exhaust airstream downstream of where the first quantityof heat is transferred to the exhaust airstream.

Further, in some embodiments, the cooling of the supply airstreamdownstream of the transferring of the first quantity of heat includesremoving an eighth quantity of heat from the supply airstream andrejecting the eighth quantity of heat to the exhaust airstream, forexample, downstream of the transferring of the first quantity of heat tothe exhaust airstream. For example, in a number of embodiments, the thecooling of the supply airstream downstream of the transferring of thefirst quantity of heat includes operating a primary direct-expansionrefrigeration circuit that includes at least one primary circuitcompressor, a primary circuit evaporator coil located in the supplyairstream, and a primary circuit condenser coil located in the exhaustairstream, for instance, downstream of where the first quantity of heatis transferred to the exhaust airstream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an example of an air conditioning unit, HVACunit, or system for controlling temperature and humidity within a spacein a building that illustrates a number of embodiments of the invention;

FIG. 2 is a block diagram of an example of a prior art air conditioningunit, HVAC unit, or system for controlling temperature and humiditywithin a space in a building, illustrating a prior art problem ofcondensation within the unit or system, for example, at thedehumidification wheel, when supply air with a low dew point isproduced;

FIG. 3 is a block diagram of an example of an air conditioning unit,HVAC unit, or system for controlling temperature and humidity within aspace in a building, that illustrates certain embodiments of theinvention, and that illustrates how the prior art problem ofcondensation within the unit or system (e.g., illustrated in FIG. 2),for example, on the dehumidification wheel, can be overcome whileproducing supply air with an even lower dew point;

FIG. 4 is a block diagram of the example of FIG. 2 of the prior art airconditioning unit, HVAC unit, or system for controlling temperature andhumidity within a space in a building, illustrating a prior art problemof condensation within the unit when there is substantial flowimbalance;

FIG. 5 is a psychometric chart illustrating limitations of the prior artair conditioning unit, HVAC unit, or system of FIGS. 2 and 4;

FIG. 6 is a block diagram of the example of FIG. 3 of the airconditioning unit, HVAC unit, or system for controlling temperature andhumidity within a space in a building, that illustrates certainembodiments of the invention, and that illustrates how the prior artproblem of condensation within the unit or system, when there issubstantial flow imbalance (e.g., illustrated in FIG. 4) can beovercome;

FIG. 7 is a block diagram of the example of FIGS. 3 and 6 of the airconditioning unit, HVAC unit, or system for controlling temperature andhumidity within a space in a building, that further illustrates how theprior art problem of condensation within the unit when there issubstantial flow imbalance (e.g., illustrated in FIG. 4) can be overcomeby certain embodiments of the invention while delivering an even lowerdew point than shown in FIG. 6;

FIG. 8 is a psychometric chart illustrating performance of the airconditioning unit, HVAC unit, or system of FIGS. 3, 6, and 7;

FIG. 9 is a block diagram of the example of FIGS. 3, 6, and 7 of the airconditioning unit, HVAC unit, or system for controlling temperature andhumidity within a space in a building, that illustrates how the unit orsystem can perform when there is no primary cooling (e.g., when theprimary cooling coil chilled water or primary direct expansion circuitis turned off);

FIG. 10 illustrates an example of an equipment layout for certainembodiments of the invention;

FIG. 11 is a plan view of an example of an air conditioning unit, HVACunit, or system for controlling temperature and humidity within a spacein a building that illustrates several embodiments of the inventionhaving a primary direct expansion refrigeration circuit with thecondenser coil located in the exhaust airstream;

FIG. 12 is a flow chart illustrating an example of method forcontrolling temperature and humidity within a space in a building, and

FIG. 13 is a flow chart illustrating another example of method forcontrolling temperature and humidity within a space in a building.

The drawings and written materials provided herewith illustrate, amongother things, examples of certain aspects of particular embodiments.Other embodiments, however, may differ. Various embodiments may includeaspects shown in the drawings, described in the specification (includingthe claims), known in the art, or a combination thereof, as examples.

DETAILED DESCRIPTION OF EXAMPLES OF EMBODIMENTS

This patent application describes, among other things, examples ofcertain embodiments, and certain aspects thereof. Other embodiments maydiffer from the examples described in detail herein. Various embodimentsinclude systems for controlling temperature and humidity, for example,within a space in a building. Such systems can be or include, forexample, air conditioning units or HVAC units. FIGS. 1, 3, 5, 6, 7, 9,10 and 11 illustrate examples of systems for controlling temperature andhumidity, for example, within a space in a building, air conditioningunits, or HVAC units. In many embodiments, such a unit or system (e.g.,100, 300, 1000, or 1100) includes a recovery heat exchanger, forexample, a recovery wheel (e.g., 110, 310, or 1010), a (e.g., passive)dehumidification wheel (e.g., 130, 330, or 1030), a primary cooling coil(e.g., 150, 350, 1050, or 1150), a secondary cooling coil (e.g., 160,360, or 1060), and a heating coil (e.g., 140, 340, or 1040), forexample, a condensing coil.

Further, in various embodiments, the unit or system forms a supplyairstream (e.g., 335 shown in FIG. 3 or 1135 shown in FIG. 11) thatpasses outdoor air (e.g., 305) first through the recovery heat exchangeror recovery wheel (e.g., 110 or 310), then through the primary coolingcoil (e.g., 150, 350, or 1150), then through the secondary cooling coil(e.g., 160 or 360), then through the dehumidification wheel (e.g., 130or 330), and then to the space. In many embodiments, the supplyairstream (e.g., 335 or 1135) starts as outdoor air (e.g., 305), andthen is cooled, dehumidified, and partially reheated, for example, bythe recovery heat exchanger or recovery wheel (e.g., 110 or 310), theprimary cooling coil (e.g., 150, 350, or 1150), the secondary coolingcoil (e.g., 160 or 360), and the dehumidification wheel (e.g., 130 or330) to become supply air (e.g., 337) that is delivered to the space.Still further, in a number of embodiments, the system (e.g., 300 or1100) forms an exhaust airstream (e.g., 315 or 1115) that passes exhaustair or return air (e.g., 345 or 1145), for example, from the space,first through the heating coil (e.g., 140 or 340, for example, thesecondary condensing coil), then through the dehumidification wheel(e.g., 130 or 330), and then through the recovery wheel (e.g., 110 or310), for example. In this context, the words “first” and “then” areused to describe the order in which a particular portion of air, of manysuch portions, passes through various pieces of equipment in theparticular embodiment described. It should be understood, however, thatdifferent portions of the air pass through these different pieces ofequipment simultaneously. Further, where an airstream is describedherein as passing through various pieces of equipment in a particularorder, it should be understood that different parts of the airstream maybe passing through the various pieces of equipment at the same time, butthat the order in which a particular portion of air passes through thevarious pieces of equipment is what is being described.

In different embodiments, the heating coil (e.g., 140 or 340) is orincludes a waste-heat heating coil (e.g., a condensing coil for an airconditioning unit or cycle, for instance, 125 or 325). Further, manyembodiments include a secondary direct-expansion refrigeration circuit(e.g., 125 or 325), for instance, that includes (e.g., among otherthings) a secondary direct-expansion refrigeration circuit compressor(e.g., 120, 320, or 1020), a secondary direct-expansion refrigerationcircuit evaporator coil (e.g., 160 or 360), a secondary direct-expansionrefrigeration circuit condenser coil (e.g., 140 or 340), or acombination thereof. In some embodiments, for example, the trim coil orsecondary cooling coil is or includes the secondary direct-expansionrefrigeration circuit evaporator coil (e.g., 160 or 360). Still further,in some embodiments, the heating coil is or includes the secondarydirect-expansion refrigeration circuit condenser coil (e.g., 140 or340), for example. Heat from the condenser of an air conditioningcircuit that is used primarily for cooling is an example of waste heat,but in some other embodiments, other sources of waste heat can be used.Further, in some embodiments, a direct-expansion refrigeration circuitcan reject heat to a location other than to the return air (e.g., 345 or1145) or exhaust airstream (e.g., 315 or 1115), such as to outdoor airoutside the building or to a geothermal heat sink, as examples. But inmany such embodiments, a remote condensing section is required and itmay be necessary to route refrigerant lines a considerable distance tothe condenser. Embodiments that include a secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) with a secondarydirect-expansion refrigeration circuit condenser coil (e.g., 140 or 340)that rejects heat to the return air (e.g., 345 or 1145) or exhaustairstream (e.g., 315 or 1115) can allow for much shorter refrigerantlines. Further still, in a number of embodiments, the dehumidificationwheel (e.g., 130 or 330) is a desiccant-based or passivedehumidification wheel, or both. In some embodiments, bypass dampers areprovided, for example, for the dehumidification wheel, to bypass thewheel when the wheel is not needed.

In various embodiments, the system (e.g., 100, 300, or 1100) forms asupply airstream (e.g., 335 or 1135) that passes outdoor air (e.g.,305), for example, first through the recovery heat exchanger or recoverywheel (e.g., 110 or 310), then through the primary cooling coil (e.g.,150, 350, or 1150), then through the secondary direct-expansionrefrigeration circuit evaporator coil (e.g., 160 or 360), then throughthe dehumidification wheel (e.g., 130 or 330), and then to the space.Even further, in many embodiments, the system (e.g., 100, 300, or 1100)forms an exhaust airstream (e.g., 315 or 1115) that passes return air(e.g., 345 or 1145) from the space first through the secondarydirect-expansion refrigeration circuit condenser coil (e.g., 140 or340), then through the dehumidification wheel (e.g., 130 or 330), andthen through the recovery heat exchanger or recovery wheel (e.g., 110 or310). In a number of embodiments, passing the return air (e.g., 345 or1145) from the space first through heating coil (e.g., 140 or 340) orthe secondary direct-expansion refrigeration circuit condenser coil(e.g., 140 or 340), and then through the (e.g., desiccant-based)dehumidification wheel (e.g., 130 or 330) preheats the exhaust airstream(e.g., 315 or 1115) or return air (e.g., 345 or 1145) entering thedehumidification wheel (e.g., 130 or 330) and reduces the relativehumidity of the exhaust airstream (e.g., 315 or 1115) that passesthrough the dehumidification wheel (e.g., 130 or 330), which thenremoves moisture from the dehumidification wheel (e.g., 130 or 330) moreeffectively. In some embodiments, this can result in an improvement indehumidification capacity (e.g., of 10 to 25 percent) with, in someembodiments, the same or similar temperature of the supply airstream(e.g., 335 or 1135) leaving the secondary cooling coil (e.g., 160 or360) or secondary direct-expansion refrigeration circuit (e.g., 125 or325) evaporator coil (e.g., 160 or 360).

In many embodiments, the recovery heat exchanger is a recovery wheel(e.g., 110 or 310). In other embodiments, however, the recovery heatexchanger is a plate-type air to air heat exchanger, as an example, or adifferent type of heat exchanger. Where a recovery wheel is describedherein, other embodiments utilize instead a recovery heat exchangergenerally, which can be a recovery wheel (e.g., 110 or 310), aplate-type air to air heat exchanger, or a different type of heatexchanger. Further, where a recovery wheel is described herein, aplate-type air to air heat exchanger is specifically contemplated inother particular embodiments. In a number of embodiments, when operatingin a cooling mode, the recovery wheel (e.g., 110 or 310) transferssensible heat from the outdoor air (e.g., 305) of the supply airstream(e.g., 335 or 1135) to the exhaust airstream (e.g., 315 or 1115).Further, in some embodiments, the recovery wheel (e.g., 110 or 310) is atotal energy recovery wheel, for example, that includes a desiccantcoating. In various embodiments, under appropriate conditions (e.g.,when operating in a cooling mode with sufficient outdoor air humidity,or when operating in a dehumidification mode), the recovery wheel (e.g.,110 or 310) transfers moisture from the outdoor air (e.g., 305) of thesupply airstream (e.g., 335 or 1135) to the exhaust airstream (e.g., 315or 1115).

In a number of embodiments, the system (e.g., 100, 300, or 1100)includes a supply fan (e.g., 113, 313, or 1113), for example, located inthe supply airstream (e.g., 335 or 1135), that moves the outdoor air(e.g., 305) first through the recovery wheel (e.g., 110 or 310), thenthrough the primary cooling coil (e.g., 150, 350, or 1150), then throughthe secondary cooling coil or secondary direct-expansion refrigerationcircuit evaporator coil (e.g., 160 or 360), then through the (e.g.,desiccant-based, passive, or both) dehumidification wheel (e.g., 130 or330), and then to the space. In particular embodiments, for example, thesupply fan is located in the supply airstream, for example, between thedehumidification wheel and the space. In other embodiments, as anotherexample (e.g., as shown), the supply fan (e.g., 113, 313, or 1113) is inthe supply airstream (e.g., 335 or 1135) between the recovery wheel(e.g., 110 or 310) and the primary cooling coil (e.g., 150, 350, or1150). Further, in various embodiments, the system (e.g., 300) includesan exhaust fan (e.g., 312), for example, located in the exhaustairstream (e.g., 315), that moves the return air (e.g., 345) from thespace first through the heating coil or (e.g., secondarydirect-expansion refrigeration circuit condenser coil (e.g., 340), thenthrough the dehumidification wheel (e.g., 330), and then through therecovery wheel (e.g., 310). In some embodiments, for example, theexhaust fan (e.g., 312) is located in the exhaust airstream (e.g., 315)downstream of the recovery wheel (e.g., 310). In this context, as usedherein, “downstream” is relative to the direction of flow of the exhaustairstream (e.g., 315). FIG. 1 also shows exhaust fan 112, which issimilarly located.

In many embodiments, the system (e.g., 100 or 300) further includes aprimary chiller (not shown), for example, that chills cooling water thatpasses through the primary cooling coil (e.g., 150 or 350). In someembodiments, the primary chiller includes multiple chillers. Moreover,in various embodiments, the primary chiller is separate from thesecondary direct-expansion refrigeration circuit system (e.g., 125 or325) or compressor (e.g., 120 or 320), or from both.

Further, various embodiments further include a partition (e.g., 111 or311 shown in FIGS. 1, 3, 6, and 11), for instance, (e.g., with referenceto FIGS. 3 and 11) between the supply airstream (e.g., 335 or 1135) andthe exhaust airstream (e.g., 315 or 1115). In a number of embodiments,for example, the recovery wheel (e.g., 310) is located in a firstopening (e.g., 601 shown in FIG. 6) in the partition (e.g., 311), the(e.g., passive) dehumidification wheel (e.g., 330) is located in asecond opening (e.g., 602) in the partition (e.g., 311), or both (e.g.,as shown). In various embodiments, the partition (e.g., 111 or 311) is awall, for example, within the system or air conditioning or HVAC unit(e.g., 100, 300, or 1100), that separates the two airstreams. In someembodiments, for example, the partition (e.g., 111 or 311) is sheetmetal. In particular embodiments, for instance, the partition (e.g., 111or 311) is insulated or includes a layer of insulation.

In various embodiments, at least adjacent to the partition (e.g., 111 or311), the supply airstream (e.g., 335 or 1135) and the exhaust airstream(e.g., 315 or 1115) travel in substantially parallel directions (e.g.,as shown). Further, in many embodiments, at least adjacent to thepartition (e.g., 111 or 311), the supply airstream (e.g., 335 or 1135)and the exhaust airstream (e.g., 315 or 1115) travel in substantiallyopposite directions (e.g., as shown). As used herein, when referring toan angle, “substantially” means to within 10 degrees. In someembodiments, however, at least adjacent to the partition (e.g., 111 or311), the supply airstream (e.g., 335 or 1135) and the exhaust airstream(e.g., 315 or 1115) travel in parallel directions, in oppositedirections, or both, to within 1, 2, 3, 5, 7, 15, 20, or 25 degrees, asother examples. Moreover, as used herein “parallel directions” includes“opposite directions” (e.g., parallel but opposite).

Still further, in various embodiments, the system or unit furtherincludes an enclosure (e.g., an air conditioning unit enclosure), forexample, that contains the recovery wheel (e.g., 110 or 310), thedehumidification wheel (e.g., 130 or 330), the primary cooling coil(e.g., 150, 350, or 1150), the secondary cooling coil (e.g., 160 or360), the secondary direct-expansion refrigeration circuit (e.g., 125 or325), the secondary circuit evaporator coil (e.g., 160 or 360), theheating coil or secondary direct-expansion refrigeration circuitcondenser coil (e.g., 140, 340, or 1140), at least part of the supplyairstream (e.g., 335 or 1135), at least part of the exhaust airstream(e.g., 315 or 1115), or a combination (e.g., all) thereof (e.g., asshown). FIGS. 1 and 11, for example, show enclosure 101. In someembodiments, for further example, the enclosure (e.g., 101) contains thepartition (e.g., 111). In many embodiments, for example, the enclosure(e.g., 101) is or includes sheet metal and has, for example, multipledoors or removeable access panels for access therein (e.g., as shown).In particular embodiments, for instance, the enclosure (e.g., 101) isinsulated (e.g., in whole or in part) or includes a layer of insulation.In certain embodiments, part or all of the enclosure is part of thebuilding (e.g., walls, floor, etc.). Further still, in variousembodiments, the partition (e.g., 111) extends to or connects to theenclosure (e.g., 101), for instance, as shown. Even further, in someembodiments, the enclosure (e.g., 101) further contains the supply fan(e.g., 113 shown in FIG. 1), the exhaust fan (e.g., 112), or both (e.g.,as shown). Even further still, in some embodiments, the enclosure (e.g.,101) further contains the secondary direct-expansion refrigerationcircuit (e.g., 125), for example, including the secondarydirect-expansion refrigeration circuit compressor (e.g., 120). In anumber of embodiments, the secondary direct-expansion refrigerationcircuit compressor (e.g., 120 or 320) is located in the exhaustairstream (e.g., 315 or 1115).

In addition, in some embodiments, the system or unit includes a primaryheating coil, for instance, located in the supply airstream, forexample, for heating the supply airstream when operating the system in aheating mode. In some embodiments, the primary heating coil is inaddition to the primary cooling coil (e.g., 150, 350, or 1150). In anumber of embodiments, for example, the enclosure further contains theprimary heating coil. Moreover, in many embodiments, the system (e.g.,for controlling temperature and humidity within a space in a building)further includes ductwork, for example, supply ductwork that deliversthe supply airstream (e.g., 335 or 1135), for example, from thedehumidification wheel (e.g., 130 or 330), or the supply air (e.g., 337)to the space. In various embodiments, the ductwork is outside of theenclosure (e.g., 101), connects to the enclosure, or both, as examples.Further, in a number of embodiments, the space includes multiple zones.Still further, in some embodiments the system includes supply ductworkthat delivers the supply airstream (e.g., 335 or 1135) to (e.g., eachof) the multiple zones. Even further, in many embodiments, the ductworkincludes return ductwork, for example, that delivers the return air(e.g., 345 or 1145) from the space or zones to become the exhaustairstream (e.g., 315 or 1115).

In various embodiments, the system (e.g., for controlling temperatureand humidity within a space in a building) further includes multiplechilled beams, for example, located within the space, for instance,within the zones. Further, in a number of embodiments, the systemincludes a main chiller that chills cooling water that passes throughthe multiple chilled beams. Still further, in some embodiments, thecooling water from the main chiller also passes through the primarycooling coil (e.g., 150 or 350), for example, in parallel, or in series(e.g., first through the primary cooling coil (e.g., 150 or 350). Insome embodiments, the primary chiller and the main chiller, as describedherein, are the same chiller (or chillers) while in other embodiments,the primary chiller and the main chiller are separate chillers (or setsof chillers). Even further, in various embodiments, the multiple chilledbeams (e.g., located within the space or zones) are active chilledbeams. Further still, in a number of embodiments, the supply airstream(e.g., 335 or 1135) that passes to the space is delivered to themultiple chilled beams located within the space. Even further still, insome embodiments, the supply airstream (e.g., 335 or 1135) that passesto the space induces room air in the space over or across the coolingcoils within the multiple chilled beams, for example, enhancing coolingcapacity delivered by the multiple chilled beams. As used herein, inthis context, “over” includes along and in contact with. In someembodiments, the room air moves through passageways or between fins ofthe chilled beams, as examples.

In some embodiments in which the space includes multiple zones, each ofthe multiple zones includes at least one of the multiple chilled beams(e.g., that are located within the space). Further, in certainembodiments, the system (e.g., for controlling temperature and humiditywithin a space in a building) further includes a chilled water zonepump, for example, for each of the multiple zones. In a number ofembodiments, for instance, the chilled water zone pump circulateschilled water through at least one of the multiple chilled beams thatare located within that zone (i.e., the zone that the particular chilledwater zone pump serves). Still further, in certain embodiments, thesystem (e.g., for controlling temperature and humidity within a space ina building) further includes a chilled water temperature sensor, forexample, for each of the multiple zones, that measures temperature ofthe chilled water that passes through the (e.g., at least one of themultiple) chilled beams that are located within that zone (e.g., thezone that the particular chilled water temperature sensor serves). Evenfurther, a number of embodiments further include a chilled water controlvalve, for instance, for each of the multiple zones, that passes chilledwater from a chilled water supply header into the (e.g., at least one ofthe multiple) chilled beams, for example, that are located within thatzone (e.g., the zone that the particular chilled water control valveserves).

Various embodiments include a digital controller, for example, for eachof the multiple zones, for instance, that controls flow of chilled waterfrom the chilled water supply header into the (e.g., at least one of themultiple) chilled beams, for example, that are located within that zone.In some embodiments, the digital controller (e.g., for each of themultiple zones) limits flow of chilled water from the chilled watersupply header into the (e.g., at least one of the multiple) chilledbeams, for instance, that are located within that zone (e.g., the zonethat the particular digital controller serves). In particularembodiments, for example, the digital controller (e.g., for each of themultiple zones) limits flow of chilled water from the chilled watersupply header into the (e.g., at least one of the multiple) chilledbeams, for instance, to avoid formation of condensation on the (e.g., atleast one of the multiple) chilled beams, for example, that are locatedwithin that zone. For example, in a number of embodiments, thecontroller limits flow of chilled water from the chilled water supplyheader into the (e.g., at least one of the multiple) chilled beams tocontrol temperature of the chilled beam(s), for example, to avoid havingpart of the beam(s) drop below the dew point temperature within thespace. In various embodiments, for example, the digital controller(e.g., for each of the multiple zones) controls flow of chilled water,for example, from the chilled water supply header, into the (e.g., atleast one of the multiple) chilled beams (e.g., that are located withinthat zone) based on or in response to a measurement of the room airhumidity or dew point within the zone, for instance, at a humidistatlocated with that zone. Further, in various embodiments, the digitalcontroller (e.g., for each of the multiple zones) controls flow ofchilled water, for example, from the chilled water supply header, intothe (e.g., at least one of the multiple) chilled beams (e.g., that arelocated within that zone) to control room air temperature within thatzone, for example, in response to a measurement of the room airtemperature within the zone for instance, at a thermostat located withthat zone (e.g., in addition to controlling temperature to preventcondensation).

Further, certain embodiments (e.g., of a system for controllingtemperature and humidity within a space in a building) include ageothermal heat sink. In some embodiments, for example, heat from theprimary cooling coil (e.g., 150, 350, or 1150) is rejected to thegeothermal heat sink. Still further, some embodiments (e.g., of a systemfor controlling temperature and humidity within a space in a building)include a direct-expansion refrigeration circuit, for instance, thatuses the geothermal heat sink as a geothermal condenser in a coolingmode. Even further, in various embodiments, the direct-expansionrefrigeration circuit uses the geothermal heat sink as an evaporator ina heating mode. Further still, in some embodiments, the direct-expansionrefrigeration circuit is a primary direct-expansion refrigerationcircuit, or the system (e.g., 100 or 300) includes a primarydirect-expansion refrigeration circuit that uses the primary coolingcoil (e.g., 150 or 350) as a primary evaporator. In some embodiments,for example, the primary direct-expansion refrigeration circuit is aheat pump that both cools and heats the primary cooling coil (e.g., 150,350, or 1150) depending on whether cooling or heating of the space isdemanded (e.g., by at least one thermostat located within the space). Ina number of embodiments, when the system (e.g., 100, 300, or 1100) isoperating in a heating mode, the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) is turned off and when thesystem) is operating in a cooling mode, the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) is turned on.

Even further, in some embodiments, the secondary direct-expansionrefrigeration circuit evaporator coil (e.g., 160 or 360), the secondarydirect-expansion refrigeration circuit condenser coil (e.g., 140 or340), or both, are not in the geothermal well field. Consequently, in anumber of embodiments, since the cost of drilling geothermal wells canbe based on the amount (e.g., tons) of cooling required, having thesecondary direct-expansion refrigeration circuit evaporator coil (e.g.,160 or 360), the secondary direct-expansion refrigeration circuitcondenser coil (e.g., 140 or 340), or both, not in the geothermal wellfield, can reduce the cost of installation of the geothermal well field,for example, in comparison with other geothermal alternatives thatprovide equivalent performance (e.g., cooling, humidity removal, orboth). Even further still, in various embodiments, using a geothermalheat sink or source can be beneficial (e.g., in addition to rejecting orobtaining heat at a preferable temperature) because the air conditioningor HVAC unit can be installed indoors (e.g., entirely or to a greaterextent) since there are no condensing (e.g., in a cooling mode) fansthat need access to outdoor air.

In various embodiments, the primary cooling coil (e.g., 150, 350, or1150) is larger, transfers more heat or enthalpy, or has more rows thanthe secondary cooling coil or secondary direct-expansion refrigerationcircuit evaporator coil (e.g., 160 or 360). In some embodiments, forexample, the primary cooling coil (e.g., 150, 350, or 1150) has at leastthree times as many rows as the secondary cooling coil or secondarydirect-expansion refrigeration circuit (evaporator coil (e.g., 160 or360). In various embodiments, for further examples, the primary coolingcoil (e.g., 150, 350, or 1150) has at least 1.5, 2, 2.5, 3.5, 4, 4.5 5,6, 7, or 8 times as many rows as the secondary cooling coil or secondarydirect-expansion refrigeration circuit (evaporator coil (e.g., 160 or360). Further, in particular embodiments, the primary cooling coil(e.g., 150, 350, or 1150) has six to eight rows. In other embodiments,the primary cooling coil (e.g., 150, 350, or 1150) has four to ten rows,four to twelve rows, six to ten rows, six to twelve rows, four or morerows, five or more rows, six or more rows, seven or more rows, eight ormore rows, or ten or more rows, as other examples. In comparison, insome embodiments, the secondary cooling coil or secondarydirect-expansion refrigeration circuit evaporator coil (e.g., 160 or360) has one row. Still further, in some embodiments, the heating coilor secondary direct-expansion refrigeration circuit condenser coil(e.g., 140 or 340) has one row. In other embodiments, however, asfurther examples, the secondary cooling coil or secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) evaporatorcoil (e.g., 160 or 360) has two or three rows, the heating coil (e.g.,140 or 340) or secondary direct-expansion refrigeration circuit (e.g.,125 or 325) condenser coil (e.g., 140 or 340) has two or three rows, ora combination thereof.

Even further, in various embodiments, the primary cooling coil (e.g.,150, 350, or 1150) transfers more heat (e.g., at design or maximumcapacity, or on average) than the secondary cooling coil or secondarydirect-expansion refrigeration circuit evaporator coil (e.g., 160 or360) transfers (e.g., at design or maximum capacity or on average). Forexample, in some embodiments, the primary cooling coil (e.g., 150, 350,or 1150) transfers more than twice as much heat at maximum capacity thanthe secondary cooling coil or secondary direct-expansion refrigerationcircuit evaporator coil (e.g., 160 or 360) transfers at maximumcapacity. In other embodiments, the primary cooling coil (e.g., 150,350, or 1150) transfers more than 1.5, 1.75, 2.25, 2.5, 3, 4, 5, 6, 7,8, 9, 10, or 12 times as much heat (e.g., at design or maximum capacityor on average) than the secondary cooling coil or secondarydirect-expansion refrigeration circuit evaporator coil (e.g., 160 or360) transfers (e.g., at design or maximum capacity or on average), asfurther examples.

In various embodiments (e.g., of a system for controlling temperatureand humidity within a space in a building) in which the space includesmultiple zones, (e.g., each of) the multiple zones include a (e.g., atleast one) zone direct-expansion refrigeration circuit, for example,that includes a zone compressor, a zone indoor air coil, and a zoneoutdoor heat exchanger, for example, among other things. In someembodiments, for example, one or more zone direct-expansionrefrigeration circuits are used instead of chilled beams in some or allof the zones. Further, in some embodiments, (e.g., each or at least one)zone direct-expansion refrigeration circuit is or includes a heat pumpthat both cools and heats the space (e.g., depending on whether coolingor heating is demanded by the thermostat), for example, that both coolsand heats a single zone of the multiple zones. Still further, inparticular embodiments, each zone outdoor heat exchanger is a geothermalheat exchanger. Even further, in certain embodiments, thedirect-expansion refrigeration circuit described herein, for example,that uses the geothermal heat sink as a geothermal condenser in acooling mode that uses the geothermal heat sink as an evaporator in aheating mode, or both, includes one or more of the zone direct-expansionrefrigeration circuits.

In various embodiments, the secondary direct-expansion refrigerationcircuit (e.g., 125 or 325) is energized, for example, under control ofthe system controller (e.g., 170 shown in FIG. 1), for instance, toensure that condensation does not occur during low airflow conditions onthe return air (e.g., 345 or 1145) side, for example, on the partition(e.g., 111 or 311), for instance, resulting from pressurization needs orvariable volume operation, by increasing the relative humidity enteringand leaving the return air (e.g., 345 or 1145) side of thedehumidification wheel (e.g., 130 or 330). In many embodiments, forexample, the supply airstream (e.g., 335 or 1135) is greater (e.g., involumetric flowrate) than the exhaust airstream (e.g., 315 or 1115), forexample, to pressurize the building, for instance, to preventinfiltration through the building exterior of (e.g., warm, humid, orboth) outdoor air into the space. In various embodiments, the flow ratescan be adjusted by changing the speed of the fans (e.g., 112, 312, 113,313 or a combination thereof), for example. Various embodimentsdescribed herein allow for a wide imbalance between the supply airstream(e.g., 335 or 1135) and the exhaust airstream (e.g., 315 or 1115)without causing (e.g., any or as much) condensation formation within theexhaust airstream or, in many embodiments, limiting dehumidificationperformance (e.g., passive dehumidification wheel performance).Moreover, in various embodiments, the system controller (e.g., 170) isconfigured to operate or energize the secondary direct-expansionrefrigeration circuit compressor (e.g., 120 or 320) to ensure thatcondensation does not occur during low airflow conditions on the returnair or exhaust airstream side resulting from pressurization needs orvariable volume operation. In a number of embodiments, condensation isavoided by decreasing the relative humidity entering and leaving theexhaust airstream (e.g., 315 or 1115) side of the dehumidification wheel(e.g., 130 or 330).

Still further, in some embodiments, the system (e.g., 100, 300, or 1100)includes a system controller (e.g., controller 170 shown in FIG. 1), forexample, in particular embodiments, configured to operate the secondarydirect-expansion refrigeration circuit compressor (e.g., 120 or 320)when (e.g., whenever) the system (e.g., 100, 300, or 1100) is operatingin a cooling mode. As used herein, a controller being “configured”, toperform one or more acts under one or more conditions means that thecontroller contains software that, when executed, or circuits that whenenergized, cause the controller to direct equipment to perform the oneor more acts when the one or more conditions occur. Further, as usedherein, a controller being “configured”, to perform one or more acts toaccomplish a particular result means that the controller containssoftware that, when executed, or circuits that when energized, cause thecontroller to direct the equipment in a manner that accomplishes theparticular result. Further still, as used herein, a controller being“configured”, to perform one or more acts to control a particularvariable means that the controller contains software that, whenexecuted, or circuits that when energized, cause the controller todirect the equipment in a manner that controls the particular variable.For example, in various embodiments, the system controller (e.g., 170)is configured to modulate cooling at the primary cooling coil (e.g.,150, 350, or 1150) to control temperature of the space when operating ina cooling mode, when operating in a dehumidification mode, or both.

Still further, in many embodiments, the system controller (e.g., 170) isconfigured to modulate cooling at the primary cooling coil (e.g., 150,350, or 1150) to control temperature of the supply airstream (e.g., 335or 1135) delivered to the space when operating in a cooling mode, whenoperating in a dehumidification mode, or both. In some embodiments, forexample, the temperature of the supply airstream (e.g., 335 or 1135)delivered to the space is limited to a minimum temperature (e.g., evenif the temperature of the space is greater than the thermostat setpoint) to avoid delivering air that is uncomfortably cold to the spaceor zones. Moreover, in some embodiments, the system controller (e.g.,170) is configured to modulate cooling at the primary cooling coil(e.g., 150, 350, or 1150) to control humidity, for example, absolutehumidity, or dew point, of the space or supply air when operating in acooling mode, when operating in a dehumidification mode, or both. Forexample, in some embodiments, the system controller (e.g., 170) isconfigured to modulate cooling at the primary cooling coil (e.g., 150,350, or 1150) to control absolute humidity level or dew point of thesupply airstream delivered to the space when operating in the coolingmode or the dehumidification mode. Further, in some embodiments, thesecondary cooling circuit (e.g., 125 or 325) is modulated (e.g., aswell) to control absolute humidity level or dew point of the supplyairstream delivered to the space, for example, when operating in thecooling mode or the dehumidification mode.

Even further, in some embodiments, when the supply airstream (e.g., 335or 1135) delivered to the space is uncomfortably cold, or approachessuch a temperature, the controller (e.g., 170) or software increases thespeed of the (e.g., passive) dehumidification wheel (e.g., 130 or 330)is increased (e.g., via a variable speed drive or variable speedcontrol) to increase the amount of sensible heat that is transferredfrom the return airstream (e.g., 345 or 1145) or the exhaust airstream(e.g., 315 or 1115) to the supply airstream (e.g., 335 or 1135) to heatthe supply airstream. Further, in some embodiments, the secondarydirect-expansion refrigeration circuit condenser coil (e.g., 140 or340), when the secondary direct-expansion refrigeration circuit isoperated, raises the temperature of the return airstream, therebyproviding more reheat capacity for the modulating dehumidification wheel(e.g., 130 or 330) when in the reheat mode.

Conversely, in some embodiments, when the space is dry, the thermostatset point is exceeded (e.g., too warm when operating in a cooling mode),or both, the speed of the dehumidification wheel (e.g., 130 or 330) isdecreased (e.g., slowed or even stopped, for example, by controller 170)to decrease the amount of sensible heat that is transferred from theexhaust airstream (e.g., 315 or 1115) to the supply airstream (e.g., 335or 1135). In a number of embodiments, a controller (e.g., 170) or one ormore control algorithms (e.g., within controller 170) determine andcontrol the speed of the dehumidification wheel (e.g., 130 or 330), forexample, to control the amount of sensible heat, moisture, or both, thatis transferred from the return airstream (e.g., 345 or 1145) or theexhaust airstream (e.g., 315 or 1115) to the supply airstream (e.g., 335or 1135).

In a number of embodiments, the system controller (e.g., 170) isconfigured to modulate the rotational speed of the dehumidificationwheel (e.g., 130 or 330), for example, based on a measured temperatureof the supply airstream delivered to the space (e.g., of supply air337). Further, in a number of embodiments, the system controller (e.g.,170) is configured to modulate the rotational speed of thedehumidification wheel (e.g., 130 or 330) specifically to control thetemperature of the supply airstream delivered to the space. In variousembodiments, the system controller (e.g., 170) is configured to modulatethe rotational speed of the dehumidification wheel (e.g., 130 or 330)while the secondary circuit or secondary circuit compressor isoperating, for example. In a number of embodiments, heat from thesecondary condenser coil increases the impact that a change indehumidification wheel speed has on temperature of the supply air.

Even further, in various embodiments, the secondary direct-expansionrefrigeration circuit) compressor (e.g., 120 or 320) has avariable-speed drive (VSD). Even further still, in some embodiments, thesystem controller (e.g., 170) is configured to modulate speed of thesecondary direct-expansion refrigeration circuit compressor (e.g., 120or 320), for example, to adjust reheat capacity at the secondarycondenser coil (e.g., 140 or 340) when operating in a cooling mode, whenoperating in a dehumidification mode, or both. In various embodiments,the controller (e.g., 170) is “configured”, as used herein, withsoftware that, when executed, causes the controller to control thevarious items of equipment in the manner described. In otherembodiments, however, the controller can be “configured” through theconfiguration of the hardware that forms the controller. In someembodiments, for instance, operating the secondary direct-expansionrefrigeration circuit compressor (e.g., 120 or 320) at a higher speedwhile reducing cooling at the primary cooling coil (e.g., 150, 350), or1150, for instance, for system 300, by reducing chilled water flow tothe primary cooling coil (e.g., 350) or raising the chilled watertemperature, can increase the temperature of the supply airstream (e.g.,335) delivered to the space, in some embodiments and conditions, withouta corresponding increase in the moisture content of the supply airstreamor supply air (e.g., 337) delivered to the space.

Further still, in some embodiments, the secondary direct-expansionrefrigeration circuit compressor (e.g., 120 or 320) is a variablecapacity compressor and variable capacity drive or variable capacitycontrol (VCC) is used rather than, or in addition to, a variable-speeddrive. In various embodiments, compressor volume or displacement (e.g.,stroke) is modulated to control capacity, for example. Even furtherstill, in some embodiments, the system controller (e.g., 170) isconfigured to modulate capacity of the secondary direct-expansionrefrigeration circuit compressor (e.g., 120 or 320), for example, toadjust reheat capacity at the secondary condenser coil (e.g., 140 or340), for instance, when operating in a cooling mode, when operating ina dehumidification mode, or both. In different embodiments. VSD, VCC, orboth, are used. Moreover, in various embodiments, the system controller(e.g., 170) is configured to modulate the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) compressor (e.g., 120 or 320)(e.g., speed, capacity, or both), for example, to adjust reheat capacityat the secondary condenser coil (e.g., 140 or 340) when operating in acooling mode, when operating in a dehumidification mode, or both.

In a number of embodiments, the system controller (e.g., 170) isconfigured to lower the speed or capacity of the secondary directexpansion circuit compressor (e.g., 120 or 320) when the dew point orhumidity level in the space or supply air (e.g., 337) drops below asetpoint dew point or humidity level threshold, at least when supply airtemperature or space temperature, or both, are below a setpointtemperature threshold. In various embodiments, the system controller(e.g., 170) is configured to lower the rotational speed of thedehumidification wheel (e.g., 130 or 330), for example, and maintain thespeed or capacity of the secondary direct expansion circuit compressor(e.g., 120 or 320), when the dew point or humidity level in the space orsupply air (e.g., 337) drops below the setpoint dew point or humiditylevel threshold and the supply air temperature or space temperature (orboth) are above the temperature setpoint threshold.

Further, in a number of embodiments, the system controller (e.g., 170)is configured to increase the speed or capacity of the secondary directexpansion circuit compressor (e.g., 120 or 320) when the dew point orhumidity level in the space or supply air (e.g., 337) exceeds (e.g., thesame or a different) setpoint dew point or humidity level threshold, atleast when supply air temperature or space temperature, or both, areabove (e.g., the same or a different) setpoint temperature threshold.Moreover, in various embodiments, the system controller (e.g., 170) isconfigured to increase the rotational speed of the dehumidificationwheel (e.g., 130 or 330), for example, and maintain the speed orcapacity of the secondary direct expansion circuit compressor (e.g., 120or 320), when the dew point or humidity level in the space or supply air(e.g., 337) exceeds (e.g., the same or a different) setpoint dew pointor humidity level threshold and the supply air temperature or spacetemperature (or both) are below (e.g., the same or a different)temperature setpoint threshold.

In particular embodiments, the system controller (e.g., 170) isconfigured to operate the system (e.g., 100, 300, or 1100) in aneconomizer mode in which cooling at the primary cooling coil (e.g., 150,350, or 1150) is turned off. In some embodiments, for example, theprimary chiller or chillers that chill cooling water that passes throughthe primary cooling coil (e.g., 150 or 350), or the main chiller(s) asdescribed herein, are turned off and remain off during the economizermode. In other embodiments, the primary direct expansion refrigerationcircuit (e.g., 1122, as otherwise described herein, or other suchsystems), are turned off and remain off during the economizer mode. Invarious embodiments, however, during the economizer mode, at least whenhumidity levels warrant, the secondary direct-expansion refrigerationcircuit (e.g., 125 or 325) or compressor (e.g., 120 or 320) thereof isoperated to dehumidify the supply airstream (e.g., 335 or 1135) with thesecondary direct-expansion refrigeration circuit evaporator coil (e.g.,160 or 360), the (e.g., desiccant-based or passive) dehumidificationwheel (e.g., 130 or 330), or both. In some embodiments, the secondarycircuit is operated during the economizer mode (e.g., only) when outdoorair (e.g., 305) humidity is high enough that such dehumidification isnecessary or desirable. In such circumstances, the (e.g., smaller)secondary circuit compressor (e.g., 120 or 320) of the secondary circuit(e.g., 125 or 325) can be operated to provide the dehumidificationrather than operating the primary cooling circuit (e.g., chiller orchillers or primary direct expansion circuit or compressors). As usedherein, when a compressor or cooling is said to be turned off during aparticular mode of operation (e.g., the economizer mode), unlessindicated otherwise, the compressor or cooling is to remain off for theduration of that particular mode of operation.

Still further, in some embodiments, the system controller (e.g., 170) isconfigured to operate the system (e.g., 100, 300, or 1100) in apart-load mode in which cooling at the secondary cooling coil (e.g., 160or 360) is turned off and cooling at the primary cooling coil (e.g.,150, 350, or 1150) is modulated, for example, to dehumidify the supplyairstream (e.g., 335 or 1135) using the (e.g., desiccant-based)dehumidification wheel (e.g., 130 or 330). Even further, in someembodiments, the system controller (e.g., 170) is configured to operatethe system (e.g., 100, 300, or 1100) in a part-load or recirculationmode in which cooling at the primary cooling coil (e.g., 150, 350, or1150) is modulated down or off, and cooling the secondary cooling coil(e.g., 160 or 360) is modulated, for example, to dehumidify the supplyairstream (e.g., 335 or 1135), for instance, using the dehumidificationwheel (e.g., 130 or 330).

Further still, in a number of embodiments, the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) can providecooling when the chilled water plant or chiller is turned off, or whenthe primary direct expansion refrigeration circuit (e.g., 1122) isturned off, for example, due to temperature lockout or time of year. Insome cases, the chilled water plant may be active but the outdoor airsystem may be the only system that requires chilled water, for example,for dehumidification purposes. In such cases, especially when theambient conditions are cool, extremely cold chilled water may beproduced, for example, in low quantities, which may complicate thecontrol of the single chilled water coil. Accordingly, in someembodiments, the system controller (e.g., 170) is configured to operatethe system (e.g., 100, 300, or 1100) in a part-load mode in whichcooling at the primary cooling coil (e.g., 150, 350, or 1150) is turnedoff and the supply airstream (e.g., 335 or 1135) is cooled using thesecondary cooling coil (e.g., 160 or 360). In a number of embodiments,for example, cooling at the secondary cooling coil (e.g., 160 or 360) ismodulated, for example, by the system controller (e.g., 170) to controltemperature of the supply airstream (e.g., 335 or 1135), the space, orboth. In some embodiments, (e.g., when warranted by conditions) thesupply airstream (e.g., 335 or 1135) is dehumidified, for example, withthe secondary cooling coil (e.g., 160 or 360), the dehumidificationwheel (e.g., 130 or 330), or both, for example, in addition to orinstead of cooling with the secondary cooling coil (e.g., 160 or 360)when the primary cooling coil (e.g., 150, 350, or 1150) is turned off.Further, in certain embodiments, the system controller (e.g., 170) isconfigured to stop the (e.g., desiccant-based or passive)dehumidification wheel (e.g., 130 or 330), for example, when warrantedby conditions (e.g., when not needed to reduce humidity or to warm thesupply air). The dehumidification wheel (e.g., 130 or 330) can bestopped, for example, to avoid reheating the supply airstream (e.g., 335or 1135) after being cooled by the secondary cooling coil (e.g., 160 or360), for example, when operating in a mode where the primary coolingcoil (e.g., 150, 350, or 1150) is turned off.

Even further, in a number of embodiments, the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) can provide cooling,dehumidification, or condensation control during the startup andconstruction phase of a building. In certain embodiments, the systemcontroller (e.g., 170) is configured to operate and control (e.g.,modulate) the secondary direct-expansion refrigeration circuit (e.g.,125 or 325) to provide such cooling, dehumidification, and/orcondensation control specifically during the startup and constructionphase of the building. For example, in some embodiments, due tounconditioned areas, lack of finalized air balancing or controls, orboth, the secondary direct-expansion refrigeration circuit (e.g., 125 or325) can provide temporary cooling or dehumidification, for instance,during times when the space humidity is high or even uncontrollable.Accordingly, in some embodiments, the system controller (e.g., 170) isconfigured to operate and control (e.g., modulate) the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) to providetemporary cooling during times when the space humidity is high or evenuncontrollable, at least to design levels. Further, during such times,condensation can occur, for example, on the (e.g., passive)dehumidification wheel (e.g., 130 or 330), for instance, served by aprimary or chilled water system. In various situations, this can, forexample, damage the wheel or cause corrosion.

In a number of embodiments, the inclusion of the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325), which canraise the moisture-carrying capability of the return airstream (e.g.,345 or 1145) before the dehumidification wheel (e.g., 130 or 330),solves this problem under many conditions. Further, in particularembodiments, the system controller (e.g., 170) is configured to operateand control (e.g., modulate) the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) to prevent condensation, forexample, on the dehumidification wheel (e.g., 130 or 330) served by achilled water system, for instance, to avoid problems, for example,which can cause corrosion or damage the wheel. In various embodiments,the system controller (e.g., 170) is configured to operate and control(e.g., modulate) the secondary direct-expansion refrigeration circuit(e.g., 125 or 325) to raise the temperature of the return airstream(e.g., 345 or 1145) before the dehumidification wheel (e.g., 130 or330), for example, to prevent condensation on the dehumidification wheel(e.g., 130 or 330).

In some embodiments, the secondary direct-expansion refrigerationcircuit (e.g., 125 or 325) can be operated or modulated (e.g., by thesystem controller, for instance, 170) to deliver a warmer supply air(e.g., 337) temperature to the occupied space or active chilled beams,for example, to avoid over-cooling of the space by the primary airflowalone. When low dew points are desired, for example, colder air may berequired to be delivered to the dehumidification wheel (e.g., 130 or330) which can result in colder air leaving the dehumidification wheel.In some conditions, this reheat capability can be highly advantageous.In some embodiments, for example, the system controller (e.g., 170) isconfigured to operate the secondary direct-expansion refrigerationcircuit (e.g., 125 325) or compressor (e.g., 120 or 320), for example,to deliver a warmer supply air (e.g., 337) temperature to the occupiedspace or active chilled beams, for instance, to avoid over-cooling ofthe space by the primary airflow alone (e.g., when temperature,humidity, or both conditions warrant such operation). Further, incertain embodiments, the system controller (e.g., 170) is configured tomodulate the secondary direct-expansion refrigeration circuit (e.g., 125or 325) or compressor (e.g., 120 or 320) (e.g., speed or capacity), forexample, to deliver a warmer supply air (e.g., 337) temperature to theoccupied space or active chilled beams, for instance, to avoidover-cooling of the space by the primary airflow or to control coolingthereof.

In various embodiments, the secondary direct-expansion refrigerationcircuit (e.g., 125 or 325) or secondary compressor (e.g., 120 or 320)can be modulated down (e.g., reduced in speed or capacity), or eventurned off, when conditions within the space have a high sensible loadand low latent load, when cold air is desired from the system or unit,and when condensation on the return air (e.g., 345 or 1145) side leavingthe dehumidification wheel (e.g., 130 or 330) is not a concern, forexample. Under such conditions, cooling can be provided with the primarycooling coil (e.g., 150, 350, or 1150), for instance. Under suchconditions, the primary cooling coil (e.g., 150, 350, or 1150) may alsoprovide dehumidification, even though greater dehumidification mayresult if the secondary circuit were used. In some embodiments, forexample, the system controller (e.g., 170) is configured to turn off thesecondary direct-expansion refrigeration circuit (e.g., 125 325) orcompressor (e.g., 120 or 320) and provide cooling with the primarycooling coil (e.g., 150, 350, or 1150) when conditions within the spacehave a high sensible load and low latent load, when cold air is desiredfrom the unit, when condensation on the return air (e.g., 345 or 1145)side leaving the dehumidification wheel (e.g., 130 or 330) is not aconcern, or a combination thereof.

In particular embodiments, the system controller (e.g., 170) isconfigured to reduce the speed or capacity of the secondary compressor(e.g., 120 or 320) or reduce the capacity of the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) whenconditions within the space have a high sensible load and low latentload, when cold air is desired from the unit, when condensation on thereturn air side leaving the dehumidification wheel (e.g., 130 or 330) isnot a concern, or a combination thereof. These control strategies can bebeneficial, for example, under conditions that are relatively hot anddry. In a number of embodiments, the controller (e.g., 170) can modulatedown or turn off the secondary direct-expansion refrigeration circuit(e.g., 125 or 325) or compressor (e.g., 120 or 320), for example, inresponse to space temperature relative to one or more thermostatsetpoints, and one or more humidity or dew point measurements, forexample.

In many projects, for example, in many schools, there is a need ordesire to maintain space humidity during unoccupied hours. Further, in anumber of situations, the number of these hours can be substantial.Accordingly, various embodiments provide an unoccupied mode whereminimal outdoor air (e.g., 305), and thereby cooling load, is required.In a number of embodiments, under these conditions, the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) can beoperated to perform dehumidification, for example, in some embodiments,all of the dehumidification needs, without the need for operating theprimary chilled water, direct expansion (e.g., 1122), or heat pumpcircuit. In some embodiments, for example, the system controller (e.g.,170) is configured to operate or modulate the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) or compressor (e.g., 120 or320) to maintain space humidity during unoccupied hours or to provide anunoccupied mode where minimal outdoor air (e.g., 305), and therebycooling load, is required (e.g., or both). In a number of embodiments,the system controller (e.g., 170) is configured to operate or modulatethe secondary direct-expansion refrigeration circuit (e.g., 125 or 325)or compressor (e.g., 120 or 320) (e.g., during unoccupied periods, underappropriate conditions, or both) to perform dehumidification (e.g., allof the dehumidification needs), for instance, without operating (e.g.,while turning off and leaving turned off) the primary cooling coil(e.g., 150, 350, or 1150) (e.g., chilled water, direct expansion, orheat pump circuit).

In various situations where the primary cooling coil (e.g., 150 or 350)or circuit (e.g., chiller or chillers) is operated to providedehumidification, however, under such conditions, other cooling at thespace may not be needed so the chiller may be operated at a low load andproblems can be encountered maintaining a desired or consistent coolingwater temperature. For example, in some conditions where a cooling watertemperature of 42 degrees was desired, the chilled water temperaturefluctuated between 36 and 40 degrees, as examples, which caused problemscontrolling the air temperature from the primary cooling coil. In anumber of embodiments that have a secondary (e.g., refrigeration)circuit, however, the primary cooling coil (e.g., 150 or 350) is notused at all under certain low-cooling-demand circumstances or when onlydehumidification is required, and air temperature can be easier tocontrol, can be controlled more precisely, or both.

Still further, in a number of embodiments, conditions can exist wherethe primary cooling coil (e.g., 150, 350, or 1150) (e.g., chiller orchillers or direct expansion system, for instance, 1122) is needed tocool outdoor air (e.g., 305) introduced to the space but other coolingat the space (e.g., chilled beams or zone direct expansion units, suchas geothermal units) are not needed to provide further cooling. Variousembodiments provide cooling of outdoor air (e.g., 305) at the primarycooling coil (e.g., 150, 350, or 1150) under such circumstances withoutproviding other cooling at the space. Even further, in some embodiments,the system (e.g., 100, 300, or 1100) or unit can be operated in anunoccupied mode. In particular embodiments, for example, air isrecirculated within the system or unit in an unoccupied mode. Moreover,in various embodiments, an unoccupied mode can include, at least undercertain circumstances, using the secondary (e.g., direct-expansionrefrigeration) circuit alone (i.e., without cooling at the primarycooling coil (e.g., 150, 350, or 1150). In various applications, lesssensible cooling is required when the building is unoccupied, but somelevel of dehumidification, (e.g., less than when the building isoccupied) may be required or desirable. In a number of embodiments, thesecondary direct-expansion refrigeration circuit (e.g., 125 or 325) canprovide such dehumidification.

An example of a dehumidification wheel (e.g., 130 or 330), as usedherein, is a passive dehumidification wheel. As used herein a “passivedehumidification wheel” is a dehumidification wheel that transfers asignificant quantity of moisture from the supply airstream (e.g., 335 or1135) chilled by the primary cooling coil (e.g., 150, 350, or 1150) tothe exhaust airstream (e.g., 315 or 1115) without the exhaust airstreambeing heated to promote regeneration of the dehumidification wheel.Dehumidification wheels 130 and 330 are passive dehumidification wheelsin many embodiments. Further, as used herein, the “passivedehumidification wheel” (e.g., 130 or 330) is one that provides moistureremoval from the (e.g., saturated or near saturated) supply airstream(e.g., 335 or 1135) leaving the primary (e.g., 150, 350, or 1150) orsecondary cooling coil (e.g., 160 or 360) when operated, with or withoutthe modest added heat provided, for example, by the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) condenser coil(e.g., 140 or 340) located in the return airstream (e.g., 345 or 1145).In many embodiments, for example, the adsorbed moisture contained withinthe passive (e.g., desiccant) wheel is removed (i.e., regenerated), orcan be, by using the lower relative humidity air contained within thereturn or exhaust airstream (e.g., 315 or 1115) alone.

In many embodiments, the dehumidification wheel (e.g., 130 or 330)regenerates when removing moisture from the (e.g., saturated or nearsaturated) supply airstream (e.g., 335 or 1135) with exhaust air (e.g.,315 or 1115) returned from the space that is at a temperature below 95degrees F. In other embodiments, the dehumidification wheel (e.g., 130or 330) regenerates when removing moisture from the (e.g., saturated ornear saturated) supply airstream (e.g., 335 or 1135) with exhaust air(e.g., 315 or 1115) returned from the space that is at a temperaturebelow 100, 97, 93, or 90 degrees F., as other examples. Further, in manyembodiments, the dehumidification wheel (e.g., 130 or 330) regenerateswithout the regenerating airstream (e.g., exhaust airstream 335 or 1135)having been heated with a burner that burns a fuel. Further still, inmany embodiments, the dehumidification wheel (e.g., 130 or 330)regenerates without the regenerating airstream (e.g., exhaust airstream335 or 1135) having been heated to a temperature that exceeds 95 degreesF. Still further, in various embodiments, the dehumidification wheel(e.g., 130 or 330) regenerates without the regenerating airstream (e.g.,exhaust airstream 335 or 1135) having been heated to a temperature thatexceeds 100, 97, 93, or 90 degrees F., as other examples. Even further,in many embodiments, heat from the secondary condenser coil (e.g., 140or 340) is the only heat added to the return air (e.g., 345 or 1145)after the return air leaves the space but before the return air is usedto regenerate the dehumidification wheel (e.g., 130 or 330). In fact, invarious embodiments, no heat other than the heat from the secondarycondenser coil (e.g., 140 or 340) is added to the return air (e.g., 345or 1145) between the time that the return air leaves the space and thereturn air is used to regenerate the dehumidification wheel (e.g., 130or 330). In further embodiments, no substantial heat other than the heatfrom the secondary condenser coil (e.g., 140 or 340) is added to thereturn air (e.g., 345 or 1145) between the time that the return airleaves the space and the return air is used to regenerate thedehumidification wheel (e.g., 130 or 330). In this context,“substantial” means enough to raise the temperature of the air by morethan five degrees. In other embodiments, no heat other than the heatfrom the secondary condenser coil (e.g., 140 or 340) is added to thereturn air (e.g., 345 or 1145) between the time that the return airleaves the space and the return air is used to regenerate thedehumidification wheel (e.g., 130 or 330) that is enough heat to raisethe temperature of the return air by more than 4, 6, 8, 10, 12, or 15degrees, as other examples.

Further, in a number of embodiments, there are times when it isbeneficial (e.g., for higher energy efficiency during part loadconditions) to operate the system or unit (e.g., 100, 300, or 1100)without operating the secondary direct-expansion refrigeration circuit(e.g., 125 or 325), or the compressor thereof (e.g., 120 or 320). Stillfurther, in some embodiments, the system (e.g., 100, 300, or 1100),unit, or controller (e.g., 170) is configured (e.g., programmed) tooperate the system or unit without operating the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) or compressor(e.g., 120 or 320), cooling the supply airstream (e.g., 335 or 1135) atthe secondary direct-expansion refrigeration circuit evaporator coil orsecondary cooling coil (e.g., 160 or 360), or heating the exhaustairstream (e.g., 315 or 1115) at the secondary direct-expansionrefrigeration circuit condenser coil or heating coil (e.g., 140 or 340),for example, under part load conditions. In many embodiments, thesystem, unit, or controller is configured to turn off the secondarycircuit when it is beneficial to do so (e.g., when dehumidification oradditional dehumidification from the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) or secondary cooling coil(e.g., 160 or 360) and dehumidification wheel (e.g., 130 or 330) is notneeded or desirable). In various embodiments, control algorithmsdetermine when the secondary direct-expansion refrigeration circuit(e.g., 125 or 325) is on or, in some embodiments, is modulated, duringcooling or dehumidification modes (or both).

Further still, where passive dehumidification wheels (e.g., 130 or 330)are described herein, other embodiments, an active dehumidificationwheel is another alternative that is contemplated. Adding significantadditional regenerative heat can, however, among other things, reduce oreliminate the benefit of the recovery wheel (e.g., 110 or 310), at leastin a number of the equipment configurations described herein, or in somecircumstances. For this and other reasons, including the need foradditional regenerative heat for an active dehumidification wheel,various embodiments described herein use a passive dehumidificationwheel (e.g., 130 or 330) rather than an active dehumidification wheel.As mentioned, however, other embodiments may differ.

In many embodiments where the primary cooling coil, for instance, 150 or350, is cooled with chilled water, the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) can be used to deliver colderair than would be possible with a chilled water system alone due to thetemperature limitation of the chilled water available. In particularembodiments, this allows air that is colder or that has a lower dewpoint (or both) to be produced and delivered, for example, inconjunction with the dehumidification wheel (e.g., 130 or 330). Asdescribed, in chilled water systems, the minimum temperature that theair leaving the cooling coil (e.g., 150 or 350) can reach has beenlimited by how cold the chilled water can be produced using traditionalchiller performance limitations. As a result, the minimum temperatureand the amount of humidity that can be removed from the outdoor air(e.g., 305) are limited. Lower levels of humidity in the supply air(e.g., 337), however, can be beneficial in some situations, for example,where chilled beams are used. In some embodiments, for example, thesystem controller (e.g., 170) is configured to operate the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) to delivercolder air than would be possible with a chilled water system alone, forexample, due to the temperature limitation of the chilled wateravailable. In various embodiments, the system controller (e.g., 170) isconfigured to operate the secondary direct-expansion refrigerationcircuit (e.g., 125 or 325) to allow air that is colder or that has alower dew point (or both, in a number of embodiments) to be produced anddelivered, for example, in conjunction with the dehumidification wheel(e.g., 130 or 330, for instance, in comparison with a system havingchilled water that does not have a secondary direct expansion circuit),for example, as shown in FIGS. 2 and 4.

In many situations, it is beneficial for components of the system (e.g.,air conditioning or HVAC, for instance, 100, 300, or 1100) to be locatedwithin the building rather than outdoors. In a number of embodiments,the secondary circuit (e.g., 125 or 325) is (e.g., entirely) locatedwithin the building. For instance, the second stage DX evaporator coil(e.g., 160 or 360) is matched with the condenser coil (e.g., 140 or 340)contained within the building exhaust airstream (e.g., 315 or 1115). Inthis configuration, a remote condensing section, outside the building,is typically not required for the secondary circuit (e.g., 125 or 325).When chilled water is used for the first stage cooling coil (e.g., 150or 350), chilled water must be supplied, but refrigerant lines to aremote condensing section, outside the building, is typically notrequired for the first stage cooling coil (e.g., 150 or 350).

When the first cooling stage (e.g., serving primary cooling coil 150 or350) is also designed to be a direct expansion circuit or heat pump, aremote condensing section outside the building can be used, in a numberof embodiments, so that a high volume of outdoor air can be pulledacross the condensing coil and ejected to the outdoors. This approach,however, requires refrigerant lines to the remote condensing sectionoutside the building, which typically must be installed, connected,tested, and charged at the job site. In addition, in many installations,outdoor space suitable for the remote condensing section outside thebuilding may be in short supply. In some embodiments, water sourcecondensing sections are employed for the first stage cooling (e.g., atprimary coil 150 or 350), and can offer certain performance advantagesover air cooled condensing sections by providing a more moderatetemperature heat sink or source, especially when heat pump capability isutilized. Using a water source approach, however, requires drillingeither one or more geothermal wells or installing a cooling tower andinstalling a water loop, both of which require space that may not beavailable and may increase the cost of installation.

As illustrated in FIG. 11, an alternate approach in some embodimentsutilizes a first stage or primary direct expansion cooling circuit(e.g., 1122), for example, in addition to the (e.g., integrated) secondstage DX cooling circuit (e.g., 125). In many embodiments, the condensercoil (e.g., 140 or 340) for the secondary cooling circuit (e.g., 125 or325) is located within the return air or exhaust airstream (e.g., 315 or345 shown in FIG. 3, or 1115 or 1145 in FIG. 11) from the conditionedspace as described herein. In various embodiments, the unit or system(e.g., 1100) includes a primary direct-expansion refrigeration circuit(e.g., 1122) that includes the primary cooling coil (e.g., 1150) whichacts as a primary evaporator when operating in a cooling mode. In manyembodiments, the primary direct-expansion refrigeration circuit (e.g.,1122) also includes a primary condensing coil (e.g., 1104) which acts asa condenser when operating in the cooling mode, and at least one primarycompressor (e.g., 1120). In a number of embodiments, the exhaustairstream (e.g., 1115) passes through the primary condensing coil (e.g.,1104, as shown). In various embodiments (e.g., system 1100), the returnair (e.g., 1145) of the exhaust airstream (e.g., 1115) passes firstthrough the secondary circuit condenser coil (e.g., 140), then throughthe (e.g., desiccant-based) dehumidification wheel (e.g., 130), thenthrough the recovery wheel (e.g., 110), and then through the primarycondensing coil (e.g., 1104).

In some embodiments, the first stage direct expansion cooling circuit(e.g., 1122) is (e.g., totally) integrated within the enclosure (e.g.,101) of the system or unit (e.g., 1100). In the embodiment shown,condenser coil 1104 for first stage or primary circuit 1122 (e.g., ofcooling) is installed within exhaust air outlet section 1101 of system1100 allowing the existing exhaust air fan 1112 to also function as thecondenser fan. The enhanced static pressure capability associated withsuch an exhaust/condenser fan (e.g., 1112), in various embodiments,provides performance advantages over conventional, low static capabilitycondenser fans. These advantages can include, for example, the abilityto use a deeper, more efficient condensing coil (e.g., 1104) withincreased rows, tighter fins, more capacity, or a combination thereof,as examples. Another advantage, in some embodiments, is improvedperformance during frosting conditions when the first cooling stage(e.g., 1122) is operated as a heat pump (e.g., heating primary coil 1150to heat the space).

In other embodiments, both an outdoor air condensing coil and acondensing coil in the return air are used. In some embodiments,however, this requires an outdoor condensing unit, with some or all ofthe concerns described herein. In other embodiments, outdoor airdelivered to the unit or enclosure (e.g., 101, for example, deliveredwith supply air 335 or 1135) feeds the outdoor air condensing coil,before joining the exhaust airstream (e.g., 315 or 1115). In manyembodiments, the secondary circuit (e.g., 125), dehumidification wheel(e.g., 130), or both, make an integrated first stage direct expansioncooling circuit (e.g., 1122) more feasible or function better, at leastunder certain conditions. In some other configurations, the amount ofheat rejected from the condenser coil (e.g., analogous to 1104) cannotbe absorbed by the exhaust air (e.g., analogous to 1115) leaving thesystem without resulting in unacceptably high condensing temperatures.Extreme condensing temperatures can substantially reduce the compressorcooling output and efficiency and can also reduce the life of thecompressor (e.g., analogous to 1120). With many prior art systems (e.g.,shown in FIGS. 2 and 4), all of the cooling input required to achievethe necessary cooling and dehumidification is typically accomplishedusing a single, stage 1 cooling circuit. As a result, the temperatureleaving this stage 1 cooling coil needs to be low enough to satisfy thatneed (e.g., in conjunction with the dehumidification wheel) to deliverthe desired dew point. Stated more simply, the air temperature leavingthe stage 1 cooling coils of the prior art must be much lower than thatleaving the stage 1 coil (e.g., 1150) of many embodiments describedherein (e.g., system 1100), since the integrated second stage coil(e.g., 160) included in such embodiments provides the final, low dewpoint cooling necessary.

Since system 1100, for example, can deliver an air temperature off ofthe stage 1 cooling circuit (e.g., leaving primary coil 1150, cooled byprimary DX circuit 1122), that is less cold, a higher suctiontemperature can be used at the stage 1 coil (e.g., 1150), whileproviding the same performance as the systems in FIGS. 2 and 4, forexample. This increases the operating efficiency of the primary circuitcompressor(s) (e.g., 1120 in FIG. 11) and helps to offset the decreasein system efficiency associated with operating at a higher condensingtemperature (e.g., at coil 1104). Further, in many embodiments, thetotal cooling load requirement is reduced by the addition of the stage 2cooling circuit (e.g., 125) and since (e.g., in system 1100) thecondensing needs are satisfied by the return air (e.g., 1145) from thespace, the stage 1 cooling circuit (e.g., 1122) can be smaller, in anumber of embodiments, requiring fewer tons than many prior art systems(e.g., 200 shown in FIGS. 2 and 4).

Further, in many configurations (e.g., 200), the air temperatureexhausted from the system is cooler than the outdoor air temperaturesince the recovery system is not 100% efficient. Further still, in manyembodiments, the purge and seal leakage airflow volumes, often thoughtof as parasitic energy losses, increase the return airflow volumeleaving the conditioned space or through the primary condenser coil(e.g., 1104). This increase in “condenser airflow” and reduction in“condenser airflow temperature” can help to increase the operatingefficiency of system 1100, for example. When combined with the benefitof a higher suction temperature and smaller stage 1 cooling circuitpreviously described, the condensing capacity requirement can be reducedlow enough, under many conditions, to allow the exhaust airflow volume(e.g., at 1115 or through coil 1104) to be used for rejection of theheat from the primary circuit (e.g., 1122), thereby eliminating theneed, in other configurations or embodiments, for a remote condensingsection.

Still further, in some embodiments, for instance, during times ofextreme outdoor temperatures, the exhaust air temperature, airflow, orboth (e.g., at exhaust air outlet section 1101 or condenser coil 1104),in many US climatic conditions is not adequate to maintain a desirablecondensing (head) pressure (e.g., within primary direct expansioncircuit 1122) and can cause high pressure trips or premature compressor(e.g., 1120) failure, in particular embodiments, even with the benefitsdescribed herein. In some circumstances, for example, the exhaust airtemperature can be too high, the exhaust airflow (e.g., at 1115 orthrough coil 1104) can be too low, or a combination thereof. Someembodiments address this potential problem by monitoring the condensingpressure (e.g., within primary direct expansion circuit 1122, forexample, monitoring using the system controller, for example, 170), andimplementing a change that increases the system condensing side capacitywhen necessary.

An example of a way of increasing condensing side capacity (e.g., underextreme conditions) is to “flash evaporate” a fine water mist ahead(i.e., upstream) of the condenser coil (e.g., between recovery wheel 110and condenser coil 1104 in FIG. 11). This can substantially lower theair temperature entering the coil, thereby increasing condensingcapacity. Another way to increase condensing capacity is to useevaporative cooling pads in place of the flash evaporation mist (e.g.,between recovery wheel 110 and condenser coil 1104). As used herein,flash evaporation of a fine water mist, and evaporative cooler pads, areboth examples of evaporative cooling. Yet another way to increasecondensing capacity is to add outdoor air to the exhaust air, forexample, upstream of the condensing coil (e.g., between recovery wheel110 and condenser coil 1104) to increase condenser airflow. In someembodiments, such added outdoor air is cooled with evaporative cooling(e.g., in different embodiments, before or after being combined withreturn air). Further, in some embodiments that include evaporativecooling for cooling condenser air (e.g., for condenser 1104), theevaporative cooling is used even when outdoor temperatures are notextreme, but when cooling is demanded, to reduce electricity consumption(e.g., by compressor 1120) or increase capacity of the direct expansionrefrigeration circuit (e.g., 1122), or both. In certain embodiments,however, evaporative cooling can be turned off (e.g., by the systemcontroller, for example, 170) when humidity or dew point (e.g., ofoutdoor air, return air, or both) exceeds a (e.g., set) threshold.

Certain embodiments provide variable refrigerant flow (VRF), include orare used as a dedicated outdoor air supply or dedicated outdoor airsystem (DOAS), or both. Variable refrigerant flow systems, in a numberof embodiments, can provide simultaneous heating and cooling todifferent zones within one or more buildings, for example. Like a numberof embodiments of heat pump systems, however, many VRF systems do nothandle raw outdoor air very well. Many VRF systems can be highlyefficient in processing sensible (temperature) loads, but, in manycases, are less efficient or effective at handling the latent loads, forexample, associated with high density spaces, for instance, like schoolclassrooms. As a result, some embodiments serve VRF systems with adedicated outdoor air system. In a number of embodiments, for example,VRF systems are served by an outdoor air system (e.g., 1100) that candecouple the latent load from the VRF room modules so that the zone VRFcoils can handle sensible only loads and operate with higher suctiontemperatures. This can increase overall system efficiency, for example.Further, removing the latent load from the VRF modules can reduce thecooling capacity requirement and therefore size of the unit required ineach classroom, for example. This can provide many system designadvantages under various circumstances.

Still further, in many embodiments, installing smaller VRF units candecrease the installation cost due, for example, to the smaller unitsand refrigerant lines. Even further, in some embodiments, a smaller maincondensing unit can be employed. Even further still, in particularembodiments, condensate management can be reduced or eliminated sincethe latent load is partially or fully handled by the DOAS (e.g., 1100).Moreover, in many embodiments, fewer pounds of refrigerant are beingpumped through the building, addressing one substantial concernregarding this technology should there be a refrigerant leak.Additionally, one challenge facing VRF systems is efficiently deliveringthe necessary heating capacity in colder climates. In some embodiments,rotational speed of the VRF compressor is increased to increase theheating output at low ambient temperatures, for example, but limitationsstill exist and it would be highly beneficial to increase the heatingoutput available as well as the efficiency or coefficient ofperformance.

In various embodiments, two effective ways of increasing the heatingcapacity available to the conditioned spaces are to minimize the heatingcapacity required by the DOAS to condition the outdoor air and toallocate a sizeable and more effective “outdoor coil” for the VRF systemwhere a substantial airflow can be used as a heat source (e.g., cooledto obtain heat to add to the space). Some embodiments (e.g., system1100) can provide both of these enhancements. As an example, assume aschool has a wing including 10 classrooms and needs 3,000 cfm of outdoorair for ventilation purposes. Decoupling the space latent load from theindividual room VRF modules, in this example, allows classroom units,operating to handle the sensible cooling load only, to be sized for 2tons each (24,000 BTUs). A conventional DOAS (e.g., system 200 shown inFIG. 2) employing a total energy recovery wheel (e.g., 210) wouldrequire approximately 16 tons of cooling input for this example toprocess the 3,000 cfm of outdoor air from a condition of 95 degrees F.DB and 78 degrees F. WB to deliver the 50-grain supply air humiditycondition required to handle both the outdoor air and spacedehumidification load. In contrast, in a number of embodiments (e.g.,1100) where the primary condenser coil (e.g., 1104) for the first stagecircuit (e.g., 1122) is installed within the exhaust air outlet section(e.g., 1101), the primary or stage 1 cooling circuit (e.g., 1122) onlyrequires 10 tons of cooling input. As a result, the total cooling forthe school wing can be achieved with only 30 tons in this example.

Now the same school operating during the winter with the outdoor airbeing 0 degrees F. DB needs 23,000 BTUs of heat for each classroom tomaintain the set point of 70 degrees F. DB. The DOAS can deliver air toeach room at 85 degrees F. DB providing 4,860 BTUs of heat so each VRFmodule must deliver the remaining 18,140 BTUs. At 0 degrees F. DB, thetypical VRF module rated at 2 tons with an outdoor condensing unit canonly deliver 16,000 BTUs when the outdoor VRF condensing unit cannotpull heat from any other zone. As a result, the spaces would not haveadequate heating capacity. In contrast, with certain embodiments (e.g.,system 1100 shown in FIG. 11), the stage 1 cooling circuit condensingcoil (e.g., 1104) is installed within the exhaust air section (e.g.,1101) of the DOAS instead of utilizing an outdoor condensing unit. Invarious embodiments, this coil, whether outdoors or in the exhaust airsection (e.g., the latter being shown in FIG. 11), serves as acondensing coil when cooling and an evaporator coil when heating. On a0-degree F. DB day, the air over the evaporator coil (e.g., 1104) in theexhaust air section (e.g., 1101), in this example, is in the range of 15degrees F. DB since the recovery device is not 100% efficient. Thisprovides approximately 4,000 cfm of exhaust air from the dual wheel(e.g., 110 and 130) energy recovery system at the 15-degree F. DB thatpasses across the VRF evaporator coil and functions as an effective heatsource to allow the main VRF condensing section to operate moreefficiently.

In this example, adding the evaporator load associated with the 4,000cfm of air at 15 degrees F. DB with the evaporator load of the main VRFcondensing section allows for a substantial increase in heating outputat the VRF modules installed in each classroom. In this example, theheating output from a 2-ton module would be increased from approximately16,000 BTUs to the 18,140 BTUs needed. Likewise, a similar coolingseason performance enhancement is recognized in this school example whenthe condenser (e.g., 1104) in the exhaust airstream (e.g., section 1101)processes air at approximately 90 degrees F. DB as opposed to theambient 95 degrees F. DB condition is combined with the main VRFcondensing section. Further, in many embodiments, the stage 2 coolingcircuit (e.g., 125), that handles the final, lower air temperaturecooling function, allows the stage 1 cooling circuit (e.g., 1122) tooperate at a higher suction temperature and to deliver air that is lesscold. In various embodiments, this provides an excellent match with theVRF system as it operates more effectively when under these conditions.With the DOAS typically requiring 40% of the total system coolingcapacity or more, off-loading approximately 25% of the DOAS coolingcapacity requirements on to the stage 2 cooling circuit (e.g., 125)handled by a designated compressor (e.g., 120) that is not part of theVRF grid is a significant advantage in a number of embodiments. Forexample, this allows for a smaller main VRF condensing section to beutilized and reduces the size of the refrigerant lines required as wellas the quantity of refrigerant required.

In a number of embodiments, a unit or system (e.g., for controllingtemperature and humidity within a space in a building) includes arecovery wheel, a (e.g., desiccant-based) dehumidification wheel, and aprimary direct-expansion refrigeration circuit. FIG. 11 provides anexample, system 1100. In various embodiments, the primarydirect-expansion refrigeration circuit (e.g., 1122) includes, forexample, at least one primary circuit compressor (e.g., 1120), a primarycircuit evaporator coil (e.g., 1150), and a primary circuit condensercoil (e.g., 1104). Further, in a number of embodiments, the system formsa supply airstream (e.g., 1135), for instance, that passes outdoor airfirst through the recovery wheel (e.g., 110), then through the primarycircuit evaporator coil (e.g., 1150), then through the dehumidificationwheel (e.g., 130), and then to the space. Still further, in variousembodiments, the system forms an exhaust airstream (e.g., 1115), forexample, that passes return air (e.g., 1145) from the space firstthrough the dehumidification wheel (e.g., 130), then through therecovery wheel (e.g., 110), and then through the primary circuitcondenser coil (e.g., 1104).

Some such embodiments (e.g., as shown in FIG. 11) further include asecondary direct-expansion refrigeration circuit (e.g., 125), forinstance, that includes a secondary circuit compressor (e.g., 120), asecondary circuit evaporator coil (e.g., 160), and a secondary circuitcondenser coil (e.g., 140). Moreover, in a number of embodiments, thesupply airstream (e.g., 1135) passes the outdoor air first through therecovery wheel (e.g., 110), then through the primary circuit evaporatorcoil (e.g., 1150), then through the secondary circuit evaporator coil(e.g., 160), then through the dehumidification wheel (e.g., 160), andthen to the space. Further, in particular embodiments, the exhaustairstream (e.g., 1115) passes the return air (e.g., 1145) from the spacefirst through the secondary circuit condenser coil (e.g., 140), thenthrough the dehumidification wheel (e.g., 140), then through therecovery wheel (e.g., 110), and then through the primary circuitcondenser coil (e.g., 1104). Even further, in particular embodiments,the primary circuit evaporator coil (e.g., 1150) has at least threetimes as many rows as the secondary circuit evaporator coil (e.g., 160),for example.

In certain embodiments, the recovery wheel (e.g., 110) is a total energyrecovery wheel that includes a desiccant coating, the recovery wheeltransfers sensible heat between the outdoor air of the supply airstream(e.g., 1135) and the exhaust airstream (e.g., 1115), the recovery wheeltransfers moisture between the outdoor air of the supply airstream andthe exhaust airstream, or a combination thereof. Further, in particularembodiments, the (e.g., desiccant-based) dehumidification wheel (e.g.,130) is a passive dehumidification wheel, the system further includes asupply fan (e.g., 1113) located in the supply airstream (e.g., 1135)that moves the outdoor air to the space, the system further includes anexhaust fan (e.g., 1112) located in the exhaust airstream (e.g., 1115)that moves the return air from the space, or a combination thereof.Still further, in a number of embodiments, the system (e.g., 1100)includes a partition (e.g., 111), for example, between the supplyairstream (e.g., 1135) and the exhaust airstream (e.g., 1115), therecovery wheel (e.g., 115) is located in a first opening (e.g., 601shown in FIG. 6) in the partition (e.g., 111 or 311), thedehumidification wheel is located in a second opening (e.g., 602 shownin FIG. 6) in the partition, at least adjacent to the partition (e.g.,111 or 311), the supply airstream (e.g., 1135) and the exhaust airstream(e.g., 1115) travel in substantially parallel directions, at leastadjacent to the partition, the supply airstream and the exhaustairstream travel in substantially opposite directions, and the system(e.g., 1100) further includes an enclosure (e.g., 101) that contains therecovery wheel (e.g., 110), the (dehumidification wheel (e.g., 130), theat least one primary circuit compressor (e.g., 1120), the primarycircuit evaporator coil (e.g., 1150), and the primary circuit condensercoil (e.g., 1104), at least part of the supply airstream (e.g., 1135),at least part of the exhaust airstream (e.g., 1115), and the partition(e.g., 111).

Even further, in some embodiments, the system (e.g., 1100, for instance,as shown) further includes, within the enclosure (e.g., 101), thesecondary direct-expansion refrigeration circuit (e.g., 125), forexample, including the secondary circuit compressor (e.g., 120), thesecondary circuit evaporator coil (e.g., 160), the secondary circuitcondenser coil (e.g., 140), or a combination thereof. In variousembodiments (e.g., of a unit or system), the primary direct-expansionrefrigeration circuit (e.g., 1122) is a heat pump, for example, thatboth cools and heats the primary circuit evaporator coil (e.g., 1150)depending on whether cooling or heating of the space is demanded.

Further still, in some embodiments, the unit or system (e.g., forcontrolling temperature and humidity within a space in a building)includes an evaporative cooler (not shown), for example, that precoolsair entering the primary circuit condenser coil (e.g., 1104 shown inFIG. 11). In particular embodiments, for instance, the evaporativecooler is located between the recovery wheel (e.g., 110) and the primarycircuit condenser coil (e.g., 1104). Still further, in a number ofembodiments, the exhaust airstream (e.g., analogous to 1115) passesthrough the evaporative cooler. Even further, in some embodiments,supplemental outdoor air is added to the exhaust airstream. Inparticular embodiments, for example, the supplemental outdoor air passesthrough the evaporative cooler. Still further, in certain embodiments,the supplemental outdoor air passes through the primary circuitcondenser coil, for instance, after the supplemental outdoor air passesthrough the evaporative cooler. Even further still, in some embodiments,the supplemental outdoor air is added to the exhaust airstream betweenthe recovery wheel and the primary circuit condenser coil.

Some embodiments (e.g., of a system for controlling temperature andhumidity within a space in a building, for instance, as describedherein) include a variable refrigerant flow subsystem (not shown), forexample, serving multiple zones within the space. In a number ofembodiments, for example, each of the multiple zones includes a fan coilunit of the variable refrigerant flow subsystem, and the supplyairstream (e.g., described herein) provides a dedicated outdoor airsupply (DOAS) that serves the variable refrigerant flow subsystem. Aparticular example is a system (e.g., for controlling temperature andhumidity within a space in a building) that includes a variablerefrigerant flow subsystem and a dedicated outdoor air supply subsystemthat includes, a recovery wheel, a (e.g., desiccant-based)dehumidification wheel, a primary cooling coil, and at least onecondenser coil. System 1100, shown in FIG. 11, is an example of such adedicated outdoor air supply subsystem. In a number of embodiments, thevariable refrigerant flow subsystem includes multiple fan coil unitsserving multiple zones within the space. Further, in variousembodiments, the dedicated outdoor air supply subsystem (e.g., 1100)serves the multiple zones. Still further, in many embodiments, thededicated outdoor air supply subsystem forms a supply airstream (e.g.,1135) that passes outdoor air first through the recovery wheel (e.g.,110), then through the primary cooling coil (e.g., 1150), then throughthe dehumidification wheel (e.g., 130), and then to the space. Furtherstill, in various embodiments, the dedicated outdoor air supplysubsystem (e.g., system 1100) forms an exhaust airstream (e.g., 1115)that passes return air (e.g., 1145) from the space through thedehumidification wheel (e.g., 130) and then through the recovery wheel(e.g., 110), for instance, as shown. Even further, in a number ofembodiments, the exhaust airstream (e.g., 1115) also passes through theat least one condenser coil (e.g., 140 or 1104).

In some embodiments (e.g., 1100), the dedicated outdoor air supplyfurther includes a secondary direct-expansion refrigeration circuit(e.g., 125), for example, that includes a secondary circuit compressor(e.g., 120), a secondary circuit evaporator coil (e.g., 160), and asecondary circuit condenser coil (e.g., 140). Further, in someembodiments, the at least one condenser coil (e.g., described above)includes the secondary circuit condenser coil (e.g., 140). Stillfurther, in some embodiments, the exhaust airstream (e.g., 1115) passesthe return air (e.g., 1145) from the space first through the secondarycircuit condenser coil (e.g., 140), then through the dehumidificationwheel (e.g., 130), and then through the recovery wheel (e.g., 110).Further still, in many embodiments, the supply airstream (e.g., 1135)passes through the secondary circuit evaporator coil (e.g., 160). Evenfurther, in some embodiments, the supply airstream passes the outdoorair first through the recovery wheel (e.g., 110), then through theprimary cooling coil (e.g., 1150), then through the secondary circuitevaporator coil (e.g., 160), then through the (e.g., desiccant-based)dehumidification wheel (e.g., 130), and then to the space.

In a number of embodiments, the dedicated outdoor air supply (e.g.,system or subsystem 1100) further includes a primary direct-expansionrefrigeration circuit (e.g., 1122), for example, that includes at leastone primary circuit compressor (e.g., 1120), a primary circuitevaporator coil (e.g., 1150), and a primary circuit condenser coil(e.g., 1104). In various embodiments, for example, the supply airstream(e.g., 1135) passes through the primary circuit evaporator coil (e.g.,1150), the primary cooling coil is the primary circuit evaporator coil(e.g., 1150), the at least one condenser coil (e.g., described above) isor includes the primary circuit condenser coil (e.g., 1104), or acombination thereof. In some embodiments, for instance, the exhaustairstream (e.g., 1115) passes the return air (e.g., 1145) from the spacefirst through the dehumidification wheel (e.g., 130), and then throughthe recovery wheel (e.g., 110), and then through the primary circuitcondenser coil (e.g., 1104), for example, as shown. Moreover, in manyembodiments, the primary direct-expansion refrigeration circuit (e.g.,1122) is a heat pump that both cools and heats the primary circuitevaporator coil (e.g., 1104) depending on whether cooling or heating ofthe space is demanded.

In some embodiments, the dedicated outdoor air supply further includesan evaporative cooler (not shown, e.g. as described herein), forexample, that precools air entering the primary circuit condenser coil(e.g., 1104). In particular embodiments, for example, the evaporativecooler is located between the recovery wheel (e.g., 110) and the primarycircuit condenser coil (e.g., 1104), the exhaust airstream (e.g., 1115)passes through the evaporative cooler, or both. Further, in someembodiments, supplemental outdoor air (not shown) is added to theexhaust airstream of the dedicated outdoor air supply. In variousembodiments, the supplemental outdoor air passes through the evaporativecooler, the supplemental outdoor air passes through the primary circuitcondenser coil (e.g., in some embodiments, after the supplementaloutdoor air passes through the evaporative cooler), or both. Stillfurther, in a number of embodiments, supplemental outdoor air is addedto the exhaust airstream, the supplemental outdoor air passes throughthe primary circuit condenser coil (e.g., 1104), the supplementaloutdoor air is added to the exhaust airstream between the recovery wheeland the primary circuit condenser coil, or a combination thereof.

Turning now from units and systems (e.g., for controlling temperatureand humidity within a space in a building, for instance, airconditioning or HVAC units or systems) to methods, various embodimentsare or include methods, for instance, for controlling temperature andhumidity within a space, for example, in a building. In manyembodiments, such a method includes certain acts, which can be performedin different orders, or in some embodiments, some or all of which areperformed, simultaneously. Methods 1200 and 1300 shown in FIGS. 12 and13 are examples of embodiments. Different embodiments include some orall of the acts shown or described, or a combination of such acts.

Method 1200, for instance, is an example of a method of controllingtemperature and humidity within a space, for example, in a building.Method 1200 includes (e.g., simultaneous) acts of: operating a secondarydirect-expansion refrigeration circuit (e.g., act 1210, for instance,secondary circuit 125 or 325 shown in FIGS. 1, 3, and 11). In someembodiments, for example, this act (e.g., 1210) includes operating(i.e., running) a secondary compressor (e.g., 120 or 320). Further, inthe embodiment illustrated, method 1200 includes passing outdoor air(e.g., act 1220, for example, outdoor air 305 shown in FIG. 3), forexample, through various components, for instance, in a particular order(e.g., to a space). In the embodiment shown, method 1200 also includespassing return air (e.g., act 1230, for example, return air 345 or 1145shown in FIGS. 3 and 11), for example, from the space, for instance,through various (e.g., of the same or different) components, forexample, in a certain order.

In a number of embodiments, for example, the secondary direct-expansionrefrigeration circuit compressor (e.g., 120 or 320) is part of thesecondary direct-expansion refrigeration circuit (e.g., 125 or 325 ofact 1210), for instance, that includes (e.g., in addition to thesecondary direct-expansion refrigeration circuit compressor) a secondarydirect-expansion refrigeration circuit evaporator coil or secondarycooling coil (e.g., 160 or 360), and a secondary direct-expansionrefrigeration circuit condenser coil or heating coil (e.g., 140 or 340).Further, various embodiments include (e.g., in act 1220) passing outdoorair (e.g., outdoor air 305 or supply airstream 335 or 1135) firstthrough a recovery wheel (e.g., 110 or 310), then through a primarycooling coil (e.g., 150, 350, or 1150), then through the secondarydirect-expansion refrigeration circuit evaporator coil or secondarycooling coil (e.g., 160 or 360), then through a (e.g., passive)dehumidification wheel (e.g., 130 or 330), and then to the space. Forexample, in the embodiment shown in FIG. 3, act 1220 can be performedusing supply fan 113, 313, or 1113, for example, under the control ofcontroller 170 shown in FIG. 1.

Still further, a number of embodiments (e.g., of method 1200) include(e.g., in act 1230) passing return air (e.g., 345 or 1145, for instance,with exhaust fan 112, 312, or 1112) from the space or an exhaustairstream (e.g., 315 or 1115) first through the secondarydirect-expansion refrigeration circuit condenser coil, heating coil, orpreheating coil (e.g., 140 or 340), then through the (e.g., passive)dehumidification wheel (e.g., 130 or 330), and then through the recoverywheel (e.g., 110 or 310). In various embodiments, the act of passing thereturn air (e.g., 1230) from the space is performed by operating anexhaust fan (e.g., 112, 312, or 1112) that blows the return air (e.g.,345 or 1145). Further, in various embodiments the act of passing thereturn air (e.g., 1230) from the space includes exhausting the returnair (e.g., 345 or 1145), for example, to outdoors, after the return air(e.g., 345 or 1145) passes through the recovery wheel (e.g., 110 or310). In some embodiments, the exhaust airstream (e.g., 315) isexhausted to or used to ventilate another space, for example, a parkinggarage, attic, or equipment room, as other examples.

Various methods, including method 1200, further include transferringheat or moisture (e.g., in act 1240), or both, for example, betweenairstreams (e.g., supply air to exhaust air when operating in a coolingmode). Some embodiments, for example, specifically include (e.g., in act1240) transferring moisture from the outdoor air (e.g., 305) to thereturn air (e.g., 345 or 1145), for example, with a desiccant coating onthe recovery wheel (e.g., 110 or 310). Further, many embodiments include(e.g., in act 1240) transferring sensible heat from the outdoor air(e.g., 305) to the return air (e.g., 345 or 1145) with the recoverywheel (e.g., 110 or 310).

A number of embodiments further include primary conditioning (e.g., act1250 of method 1200, for instance, operating a primary cooling system,subsystem, or circuit), for example, that cools, or in some embodiments,(e.g., when demanded, for instance, in a heating mode) heats (e.g., atprimary coil 150, 350, or 1150, or at a different coil in seriestherewith), the supply airstream (e.g., 335 or 1135). In someembodiments, for example, act 1250 includes operating at least oneprimary chiller that chills cooling water, passing the cooling waterthrough the primary cooling coil (e.g., 150, 350, or 1150), or both. Onthe other hand, other embodiments include operating a primary directexpansion refrigeration circuit (e.g., 1122 shown in FIG. 11) that coolsthe primary cooling coil (e.g., 1150) and that, in the embodiment shownin FIG. 11, rejects heat through a primary condenser coil (e.g., 1104).Method 1200 is an example of such a method involving a primary directexpansion refrigeration circuit (e.g., 1122) as well, and also includesact 1260 of providing a heat source or sink, for example, to reject orobtain heat that is transferred in act 1250. Certain (e.g., of these)embodiments include, for example, passing (e.g., in act 1230) the returnair (e.g., 1145) from the space first through the secondary circuitcondenser coil (e.g., 140), then through the (e.g., passive)dehumidification wheel (e.g., 130), then through the recovery wheel(e.g., 110, for instance, performing act 1240), and then through theprimary condenser coil (e.g., 1104, performing act 1260).

Further, various methods (e.g., 1200) include controlling humidity(e.g., act 1270), for example, in the space or in the supply air (e.g.,337). In particular embodiments, controlling humidity (e.g., act 1270),or other acts of method 1200 (e.g., act 1210), can include condensingmoisture out of the outdoor air (e.g., 305 or supply airstream 335 or1135) with the secondary circuit evaporator coil (e.g., 160 or 360),transferring sensible heat to the return air with the secondary circuitcondenser coil (e.g., 140 or 340), or both, as examples. Other ways ofcontrolling humidity are described herein, including using the primarycooling coil, recovery wheel, and (e.g., passive) dehumidificationwheel.

Various embodiments involve transferring certain quantities, forexample, of heat or moisture, for instance, from particular sources toparticular destinations. Method 1300 in FIG. 13 illustrates someexamples. Method 1300 include certain acts, many of which can involvetransferring certain quantities. As used herein, a “quantity” can be arate, for example, a quantity (e.g., of energy) per unit of time, whichcan vary depending on conditions, demand, or both. In a number ofembodiments, an act involving a quantity can be steady (e.g., steadystate), but in various embodiments, the rate can vary over time, forexample, as the conditions that require the cooling, dehumidification,etc., change. Such acts can include, for example, transferring (e.g., inact 1310), a first quantity of heat. In some embodiments, for example,the first quantity of heat is transferred (e.g., in act 1310) to anexhaust airstream (e.g., 115 or 315) from outdoor air (e.g., 305)entering a supply airstream (e.g., 335 or 1135). In various embodiments,the first quantity of heat (e.g., of act 1310) can be, or can include,sensible or latent heat, or both. In a number of embodiments, the firstquantity of heat can be transferred, (e.g., in act 1310), for instance,with a recovery wheel (e.g., 110 or 310). FIGS. 3 and 6-9, includingpsychometric chart 800, provide several specific examples of quantities.FIGS. 2, 4, and 5, including psychometric chart 500, provide severalspecific examples of prior art that may be used for comparison, forexample, to illustrate differences or potential improvements.

Various methods (e.g., 1300) further include an act (e.g., 1320) ofconditioning (e.g., cooling when in a cooling mode) the supply airstream(e.g., 335 or 1135), for example, with a primary cooling coil (e.g.,150, 350, or 1150), for example, downstream of the transferring (e.g.,in act 1310) of the first quantity of (e.g., sensible or latent) heat,for instance. In some embodiments, conditioning the supply air (e.g.,act 1320) includes condensing a second quantity of moisture from thesupply airstream (e.g., 335 or 1135). As used herein, when referring toa particular airstream, “downstream” means relative to that airstream.For example, in the act (e.g., 1320) of conditioning the supplyairstream (e.g., 335 or 1135) downstream of the transferring of thefirst quantity of sensible or latent heat, “downstream” means relativeto the supply airstream (e.g., 335 or 1135).

Further, many embodiments (e.g., method 1300) include transferring(e.g., in act 1330) a third quantity of heat from the supply airstream(e.g., 335 or 1135) to return air (e.g., 345 or 1145) entering theexhaust airstream (e.g., 315 or 1115). In some embodiments, this (e.g.,act 1330) is done with a secondary direct-expansion refrigerationcircuit (e.g., 125 or 325), for example. In various embodiments, forexample, the transferring (e.g., act 1330) of the third quantity of heatfrom the supply airstream (e.g., 335 or 1135) takes place in the supplyairstream (e.g., 335 or 1135) downstream of the conditioning or cooling(e.g., act 1320) of the supply airstream (e.g., 335 or 1135, forexample, with the primary cooling coil, for instance, 150, 350, or1150). Still further, in some embodiments, the transferring of the thirdquantity of heat (e.g., In act 1330) from the supply airstream (e.g.,335 or 1135) includes condensing a fourth quantity of moisture from thesupply airstream (e.g., 335 or 1135), for example, at the secondaryevaporator coil (e.g., 160 or 360). Further, in a number of embodiments,more heat is transferred (e.g., in act 1330) to the return air (e.g.,345 or 1145) entering the exhaust airstream (e.g., 315 or 1115), forexample, at the secondary condenser coil (e.g., 140 or 340) than istransferred (e.g., in act 1330) from the supply airstream (e.g., 335 or1135), even if latent energy is considered, due to energy added bysecondary direct-expansion refrigeration circuit (e.g., 125 or 325, forinstance, by compressor 120 or 320). In some embodiments, more than thethird quantity of heat is transferred (e.g., in act 1330) to the returnair (e.g., 345 or 1145) entering the exhaust airstream (e.g., 315 or1115).

In a number of embodiments, such a method (e.g., 1300) can furtherinclude transferring (e.g., in act 1350) a fifth quantity of moisture,for example, from the supply airstream (e.g., 335 or 1135) to theexhaust airstream (e.g., 315 or 1115). In a number of embodiments, forexample, this (e.g., act 1350) can be performed, with a (e.g., desiccantbased, passive, or both) dehumidification wheel (e.g., 130 or 330). Evenfurther, in various embodiments, the transferring (e.g., in act 1350) ofthe fifth quantity of moisture from the supply airstream (e.g., 335 or1135) to the exhaust airstream (e.g., 315 or 1115) takes place in thesupply airstream (e.g., 335 or 1135) downstream of the transferring(e.g., in act 1330) of the third quantity of heat from the supplyairstream (e.g., 335 or 1135), for example, with the secondarydirect-expansion refrigeration circuit) evaporator coil (e.g., 160 or360) to the return air (e.g., 345 or 1145) entering the exhaustairstream (e.g., 315 or 1115). Further still, in various embodiments,the transferring (e.g., in act 1350) of the fifth quantity of moisturefrom the supply airstream (e.g., 335 or 1135) to the exhaust airstream(e.g., 315 or 1115) takes place in the exhaust airstream (e.g., 315 or1115) downstream of the transferring (e.g., in act 1330) of the thirdquantity of heat (e.g., with the secondary direct-expansionrefrigeration circuit condenser coil (e.g., 140 or 340) from the supplyairstream (e.g., 335 or 1135) to the return air (e.g., 345 or 1145)entering the exhaust airstream (e.g., 315 or 1115).

Even further still, in some such embodiments, in conjunction with thetransferring (e.g., in act 1350) of the fifth quantity of moisture fromthe supply airstream (e.g., 335 or 1135) to the exhaust airstream (e.g.,315 or 1115), the method (e.g., 1300) includes transferring (e.g., inact 1360) a sixth quantity of sensible heat from the exhaust airstream(e.g., 315 or 1115) to the supply airstream (e.g., 335 or 1135), forexample, with the (e.g., passive, desiccant-based, or both)dehumidification wheel (e.g., 130 or 330). As used herein, in thiscontext, “in conjunction with” means at the same location or using thesame component (e.g., with the dehumidification wheel (e.g., 130 or330). Moreover, in various such embodiments (e.g., method 1300), the act(e.g., 1360) of transferring of the sixth quantity of sensible heat(e.g., with the dehumidification wheel, for instance, 130 or 330) fromthe exhaust airstream (e.g., 315 or 1115) to the supply airstream (e.g.,335 or 1135) takes place in the supply airstream (e.g., 335 or 1135)downstream of the transferring (e.g., in act 1330) of the third quantityof heat (e.g., with the secondary direct-expansion refrigerationcircuit, for instance, 125 or 325) from the supply airstream (e.g., 335or 1135) to the return air (e.g., 345 or 1145) entering the exhaustairstream (e.g., 315 or 1115). Further, in various embodiments, thetransferring (e.g., in act 1360) of the sixth quantity of sensible heatfrom the exhaust airstream (e.g., 315 or 1115) to the supply airstream(e.g., 335 or 1135) takes place in the exhaust airstream (e.g., 315 or1115) downstream of the transferring (e.g., in act 1330) of the thirdquantity of heat from the supply airstream (e.g., 335 or 1135) to returnair (e.g., 345 or 1145) entering the exhaust airstream (e.g., 315 or1115, for example, with secondary direct-expansion refrigeration circuitcondenser coil 140 or 340).

Still further, various methods (e.g., 1300) include delivering (e.g., inact 1270) the supply airstream (e.g., 335 or 1135) to the space (e.g.,through the supply ductwork) downstream of the transferring (e.g., inact 1260) of the sixth quantity of sensible heat from the exhaustairstream (e.g., 315 or 1115) to the supply airstream (e.g., 335 or1135), for example, with the (e.g., passive) dehumidification wheel(e.g., 130 or 330). In many embodiments, the dehumidification wheel(e.g., 130 or 330) is designed and operated to maximize moisturetransfer (e.g., the fifth quantity of moisture, for instance,transferred in act 1350) and minimize heat transfer (e.g., the sixthquantity of sensible heat, for instance, transferred in act 1360). Invarious embodiments, however, the sixth quantity of sensible heat, whichincludes some of the third quantity of heat (e.g., transferred via thesecondary direct-expansion refrigeration circuit, for example, 125 or325, transferred in act 1330) provides for warmer supply air (e.g.,337), for example, cooled and dehumidified outdoor air (e.g., 305)despite a low supply air (e.g., 337) temperature prior to thetransferring (e.g., in act 1360) of the sixth quantity of sensible heatfrom the exhaust airstream (e.g., 315 or 1115) to the supply airstream(e.g., 335 or 1135, for example, with the dehumidification wheel, forinstance, 130 or 330). This can achieve a low dew point of the supplyair (e.g., 337) delivered to the space (e.g., in act 1390) and also canavoid having supply air (e.g., 337) delivered to the space that isoverly or uncomfortably cold.

Even further, in various embodiments, the transferring (e.g., in act1310) of the first quantity of (e.g., sensible or latent) heat from theoutdoor air (e.g., 305) entering the supply airstream (e.g., 335 or1135) to the exhaust airstream (e.g., 315 or 1115, for instance, withthe recovery wheel, for example, 110 or 310) takes place in the exhaustairstream (e.g., 315 or 1115) downstream of the transferring (e.g., inact 1350) of the fifth quantity of moisture from the supply airstream(e.g., 335 or 1135) to the exhaust airstream (e.g., 315 or 1115, forinstance, with the (e.g., passive) dehumidification wheel, for example,130 or 330). Further, in some embodiments, the act (e.g., 1310) oftransferring the first quantity of heat from outdoor air (e.g., 305)entering the supply airstream (e.g., 335 or 1135) to the exhaustairstream (e.g., 315 or 1115) further includes transferring a seventhquantity of moisture from the outdoor air (e.g., 305) entering thesupply airstream (e.g., 335 or 1135) to the exhaust airstream (e.g., 315or 1115), for example, downstream, relative to the exhaust airstream, ofthe transferring (e.g., in act 1350) of the fifth quantity of moisturefrom the supply airstream (e.g., 335 or 1135) to the exhaust airstream(e.g., 315 or 1115). The seventh quantity of moisture is transferred(e.g., in act 1310), in many embodiments, with a desiccant coating onthe total energy recovery wheel (e.g., 110 or 310), for example, inconjunction with transferring sensible heat. In various embodiments, theseventh quantity of moisture is transferred (e.g., in act 1310) from theoutdoor air (e.g., 305) entering the supply airstream (e.g., 335 or1135) to the exhaust airstream (e.g., 315 or 1115), downstream (withrespect to the exhaust airstream) of the dehumidification wheel (e.g.,130 or 330).

Moreover, in some embodiments, or under some conditions, theconditioning (e.g., cooling) of the supply airstream (e.g., 1135 shownin FIG. 11, for instance, in act 1320), for example, downstream of thetransferring (e.g., in act 1310) of the first quantity of heat includesremoving an eighth quantity of heat from the supply airstream (e.g., atprimary cooling coil 1150) and rejecting (e.g., in act 1328) the eighthquantity of heat, for instance, to the exhaust airstream (e.g., 1115),for example, downstream (i.e., relative to the exhaust airstream) of thetransferring (e.g., in act 1310) of the first quantity of heat to theexhaust airstream (e.g., at primary condenser coil 1104 shown in FIG.11). In various embodiments, the conditioning or cooling (e.g., in act1320) of the supply airstream (e.g., downstream, relative to the supplyairstream, of the transferring of the first quantity of heat, forexample, in act 1310) takes place at the primary cooling coil (e.g.,1150), for example.

In various embodiments, further heat (e.g., compressor energy, forinstance, from compressor 1120, that has been converted to heat by firststage or primary direct expansion refrigeration circuit 1122), inaddition to the eighth quantity of heat that was removed from the supplyairstream (e.g., 1135), is rejected (e.g., in act 1328) to the exhaustairstream (e.g., 1115), for example, downstream (i.e., relative to theexhaust airstream) of the transferring (e.g., in act 1310) of the firstquantity of heat to the exhaust airstream. Further, in a number ofembodiments, including in the embodiment illustrated, the conditioning(e.g., cooling, for example, in act 1320) of the supply airstream (e.g.,1135) downstream of the transferring (e.g., in act 1310) of the firstquantity of heat includes operating a primary direct-expansionrefrigeration circuit (e.g., 1122) that includes at least one primarycircuit compressor (e.g., 1120), a primary circuit evaporator coil(e.g., 1150) located in the supply airstream (e.g., 1135), and a primarycircuit condenser coil (e.g., 1104). In a number of embodiments, theprimary circuit condenser coil (e.g., 1104) is located in the exhaustairstream (e.g., 1115), for example, downstream (i.e., relative to theexhaust airstream) of the recovery wheel (e.g., 110) where the firstquantity of heat is transferred (e.g., in act 1310) to the exhaustairstream (e.g., 1115).

Further, various embodiments include separating the outdoor air (e.g.,305 shown in FIG. 3) or supply airstream (e.g., 335 or 1135) from thereturn air (e.g., 345 or 1145) or exhaust airstream (e.g., 315 or 1115),for example, with a partition (e.g., 111 or 311). In variousembodiments, for instance, the recovery wheel (e.g., 110 or 310) islocated in a first opening (e.g., 601 shown in FIG. 6) in the partition(e.g., 111 or 311), the (e.g., passive) dehumidification wheel (e.g.,130 or 330) is located in a second opening (e.g., 602 shown in FIG. 6)in the partition (e.g., 111 or 311), or both. Still further, variousmethods include guiding (e.g., with ductwork or walls) the outdoor air(e.g., 305) and the return air (e.g., 345 or 1145), for example, insubstantially opposite directions (e.g., as shown). Even further, anumber of embodiments include (e.g., an act of) enclosing within anenclosure (e.g., 101), the recovery wheel (e.g., 110 or 310), thedehumidification wheel (e.g., 130 or 330), the primary cooling coil(e.g., 150, 350, or 1150), the secondary direct-expansion refrigerationcircuit evaporator coil (e.g., 160 or 360), the secondarydirect-expansion refrigeration circuit condenser coil (e.g., 140 or340), or a combination thereof. In some embodiments, for example, thesecondary direct-expansion refrigeration circuit (e.g., 125 or 325) issubstantially or entirely enclosed with the enclosure, for example.Further still, various embodiments include enclosing within theenclosure the supply fan (e.g., 113, 313, or 1113) that moves theoutdoor air (e.g., 305) or supply airstream (e.g., 335 or 1135), forexample, first through the recovery wheel (e.g., 110 or 310), thenthrough the primary cooling coil (e.g., 150, 350, or 1150), then throughthe secondary cooling coil or secondary direct-expansion refrigerationcircuit evaporator coil (e.g., 160 or 360), then through thedehumidification wheel (e.g., 130 or 330), and then to the space (e.g.,in act 1390). Even further still, various embodiments include (e.g., anact of) enclosing within the enclosure (e.g., 101) the exhaust fan(e.g., 112, 312, or 1112) that moves the return air (e.g., 345 or 1145)(e.g., from the space), for instance, first through the heating coil orsecondary direct-expansion refrigeration circuit condenser coil (e.g.,140 or 340), then through the dehumidification wheel (e.g., 130 or 330),and then through the recovery wheel (e.g., 110 or 310). Moreover, someembodiments include (e.g., an act of) enclosing within the enclosure(e.g., 101) the partition (e.g., 111 or 311) that separates the outdoorair (e.g., 305) or supply airstream (e.g., 335 or 1135) from the returnair (e.g., 345 or 1145), for example, within the enclosure.

In many embodiments, the method includes (or act 1390 includes, forexample) passing the supply air (e.g., 337), supply airstream (e.g., 335or 1135), or outdoor air (e.g., 305, for example, once cooled anddehumidified, as described herein) through supply ductwork that deliversthe outdoor air (e.g., 305) or supply airstream (e.g., 335 or 1135) tothe space, for example, after the outdoor air (e.g., 305) or supplyairstream (e.g., 335 or 1135) passes through the (e.g., passive)dehumidification wheel (e.g., 130 or 330). Further, in some embodiments,the method (or act 1390) includes delivering the outdoor air (e.g., 305)or supply airstream (e.g., 335 or 1135) to multiple zones within thespace, cooling the space, for example, with multiple chilled beamslocated within the space, or both. Still further, some embodimentsinclude operating a main chiller that chills cooling water, or chillingthe cooling water, and passing the cooling water through the multiplechilled beams located within the space. Even further, in someembodiments, the method includes (or act 1250 or 1320 includes) passingthe cooling water from the main chiller (e.g., the primary chiller, or,in some embodiments, from a separate chiller) through the primarycooling coil (e.g., 150 or 350). Further still, in particularembodiments, the act of cooling the space (e.g., with multiple chilledbeams located within the space) or act 1390, as another example,includes cooling the space with active chilled beams, delivering theoutdoor air or supply air (e.g., 337) to the multiple chilled beamslocated within the space, inducing room air across the chilled beams orcooling coils within the chilled beams so as to enhance the coolingcapacity delivered to the space, or a combination thereof. For example,in certain embodiments, the act of cooling the space with the multiplechilled beams located within the space, or act 1390 of delivering thesupply air, includes moving the supply airstream (e.g., 335 or 1135)delivered to the space through slots or nozzles within the multiplechilled beams to induce room air in the space over coils within themultiple chilled beams to enhance cooling capacity provided by themultiple chilled beams.

Even further still, in certain embodiments, act 1390, or, in particularembodiments, the act of cooling the space with the multiple chilledbeams located within the space, includes cooling each of the multiplezones with at least one of the multiple chilled beams, circulatingchilled water through at least one of the multiple chilled beams, forexample, with a separate chilled water zone pump for each of themultiple zones, measuring temperature of chilled water that passesthrough the multiple chilled beams located within the space, modulatinga chilled water control valve for each of the multiple zones, passingchilled water from a chilled water supply header into the at least oneof the multiple chilled beams that are located within that zone, or acombination thereof. Moreover, in some embodiments, the method includescontrolling flow of chilled water from a chilled water supply headerinto the (e.g., multiple) chilled beams to avoid formation ofcondensation on the multiple chilled beams, using a digital controllerfor each of the multiple zones to control the flow of the chilled waterfrom the chilled water supply header into the at least one of themultiple chilled beams in that zone, controlling zone air temperature inresponse to a measurement of zone air temperature, or a combinationthereof, as examples. Other alternatives and other embodiments aredescribed herein or would be apparent to a person of ordinary skill inthe art. For example, other alternatives for cooling the space or zonesare also described herein and acts of cooling the space with otherequipment (e.g., as described herein) besides chilled beams are includedin other embodiments.

Various methods or acts, in particular embodiments, include rejectingheat (e.g., from the space) to a geothermal heat sink (e.g., in act 1260shown in FIG. 12. For example, some embodiments include rejecting heat(e.g., obtained in act 1250 or 1320) from the primary cooling coil(e.g., 150, 350, or 1150) to the geothermal heat sink. Further, certainembodiments include using a direct-expansion refrigeration circuit thatuses the geothermal heat sink as a geothermal condenser in a coolingmode. Still further, in some (e.g., heat pump) embodiments, the methodincludes using the geothermal heat sink as an evaporator in a heatingmode. Further still, in some embodiments, the method includes operatinga primary direct-expansion refrigeration circuit that uses the primarycooling coil (e.g., 150, 350, or 1150) as a primary evaporator (e.g., inact 1250 or 1320). Even further, in some embodiments, the method (e.g.,1200 or 1300) includes operating a heat pump that both cools and heatsthe primary cooling coil (e.g., 150, 350, or 1150) depending on whethercooling or heating of the space is demanded, for example, by at leastone thermostat located within the space.

Even further still, in various embodiments, the space includes multiplezones, and the method includes cooling each of the multiple zones withat least one zone direct-expansion refrigeration circuit, for example,by operating a zone compressor, cooling a zone indoor air coil, andrejecting heat from the zone through a zone (e.g., outdoor) heatexchanger, for example. In various embodiments, the act of cooling eachof the multiple zones with at least one zone direct-expansionrefrigeration circuit includes rejecting heat from the zone to ageothermal heat exchanger (e.g., the zone outdoor heat exchanger).Further, in various embodiments, for instance, each at least one zonedirect-expansion refrigeration circuits is a heat pump and the methodfurther includes heating each of the multiple zones with the at leastone zone direct-expansion refrigeration circuit by operating the zonecompressor, heating the zone indoor air coil, and obtaining heat for thezone (e.g., in act 1260) through the zone outdoor heat exchanger (e.g.,geothermal heat exchanger), for example.

In some embodiments, the method includes transferring more heat with theprimary cooling coil (e.g., 150, 350, or 1150, for instance, in act 1250or 1320), for example, at maximum capacity, than the secondary coolingcoil or secondary direct-expansion refrigeration circuit evaporator coil(e.g., 160 or 360, for instance, in act 1210 or 1330), for instance, atmaximum capacity. For example, in particular embodiments, the methodincludes transferring more than twice as much heat with the primarycooling coil (e.g., 150, 350, or 1150) at maximum capacity than thesecondary cooling coil or secondary direct-expansion refrigerationcircuit (e.g., 125 or 325) evaporator coil (e.g., 160 or 360) transfersat maximum capacity. Further, in some embodiments, the method includespassing (e.g., in act 1220) the outdoor air (e.g., 305) or supplyairstream (e.g., 335 or 1135) at a greater volumetric flowrate than thereturn air (e.g., 345 or 1145, for instance, in act 1230), for example,to pressurize the building. Further still, in some embodiments, themethod includes modulating the speed of the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) or compressor (e.g., 120 or320, for example, in act 1210, 1270, or 1330), for instance, to controlthe humidity of the air delivered to the space (e.g., in act 1390).

Even further, in some embodiments, the method includes operating (e.g.,in act 1210 or 1330) the secondary direct-expansion refrigerationcircuit (e.g., 125 or 325), or specifically, the compressor (e.g., 120or 320), for example, whenever the system (e.g., 100, 300, or 1100) isoperating (e.g., in act 1250 or 1320) in a cooling mode. Still further,in particular embodiments, the method includes modulating cooling at theprimary cooling coil (e.g., 150, 350, or 1150, for instance, in act 1250or 1320), for example, to control temperature of the space whenoperating in a cooling mode, when operating in a dehumidification mode(e.g., in act 1270), or both. Even further still, in some embodiments,the method includes modulating cooling at the primary cooling coil(e.g., 150, 350, or 1150) to control temperature of the (e.g., airconditioned) outdoor air (e.g., 305) or supply airstream (e.g., 335,1135) leaving the (e.g., passive) dehumidification wheel (e.g., 130 or330, for example, supply air 337) when operating in a cooling mode, whenoperating in a dehumidification mode, or both. Moreover, in certainembodiments, the method includes modulating (e.g., in act 1210 or 1330)the speed of the secondary direct-expansion refrigeration circuit (e.g.,125 or 325) compressor (e.g., 120 or 320) to adjust reheat capacity atthe secondary condenser coil (e.g., 140 or 340) when operating in acooling mode, when operating in a dehumidification mode (e.g., in act1270), or both.

In some embodiments, the method further includes operating in aneconomizer mode in which cooling at the primary cooling coil (e.g., 150,350, or 1150, for example, act 1250 or 1320) is turned off and thesecondary direct-expansion refrigeration circuit (e.g., 125 or 325) andcompressor (e.g., 120 or 320) is operated (e.g., in act 1210 or 1330),for example, to dehumidify (e.g., in act 1270) the outdoor air (e.g.,305) or supply airstream (e.g., 335 or 1135) with the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) orspecifically the evaporator coil (e.g., 160 or 360) and, in a number ofembodiments, with the dehumidification wheel (e.g., 130 or 330).Further, in various embodiments, the method includes transferringmoisture (e.g., in act 1240, 1270, or 1310) from the outdoor air (e.g.,305) or supply airstream (e.g., 315 or 1115) to the return air (e.g.,345 or 1145) or exhaust airstream (e.g., 315 or 1115) with the (e.g.,total energy) recovery wheel (e.g., 110 or 310).

Still further, in some embodiments, the method includes heating theoutdoor air (e.g., 305) or supply airstream (e.g., 335 or 1135) whenoperating in a heating mode using a heating coil (e.g., within theenclosure, for instance, 101) that is separate from the primary coil(e.g., 150, 350, or 1150) and that is separate from the secondarycooling coil or secondary direct-expansion refrigeration circuitevaporator coil (e.g., 160 or 360). In some embodiments, however, themethod includes heating the outdoor air (e.g., 305) or supply airstream(e.g., 335 or 1135) when operating in the heating mode (e.g., in act1250 or 1320) using the primary coil (e.g., 150, 350, or 1150) orprimary direct expansion circuit (e.g., 1122). Even further, in someembodiments, the method (e.g., 1200 or 1300) includes transferringmoisture (e.g., in act 1240, 1270, or 1350) from the outdoor air (e.g.,305) or supply airstream (e.g., 335 or 1135) to the return air (e.g.,345 or 1145) or the exhaust airstream (e.g., 315 or 1115) with thedehumidification wheel (e.g., 130 or 330). Further still, in particularembodiments, the method includes transferring sensible heat (e.g., inact 1360) from the return air (e.g., 345 or 1145) or exhaust airstream(e.g., 315 or 1115) to the outdoor air (e.g., 305) or supply airstream(e.g., 335 or 1135) with the dehumidification wheel (e.g., 130 330).

Even further still, in various embodiments, the method (e.g., 1200 or1300) includes condensing moisture out of the outdoor air (e.g., 305) orsupply airstream (e.g., 335 or 1135) with the primary cooling coil(e.g., 150, 350, or 1150, for example, in act 1220, 1250, 1270, or1320), condensing (e.g., additional) moisture out of the outdoor air(e.g., 305) or supply airstream (e.g., 335 or 1135) with the secondarycooling coil or secondary direct-expansion refrigeration circuitevaporator coil (e.g., 160 or 360, for instance, in act 1210, 1220,1270, or 1330), transferring sensible heat to the return air (e.g., 345or 1145) with the heating coil or secondary direct-expansionrefrigeration circuit condenser coil (e.g., 140 or 340, for example, inact 1210, 1230, or 1330), or a combination thereof. Moreover, in certainembodiments, the method includes transferring heat from the secondarycooling coil or secondary direct-expansion refrigeration circuitevaporator coil (e.g., 160 or 360) to the heating coil or secondarydirect-expansion refrigeration circuit condenser coil (e.g., 140 or 340)with the secondary direct-expansion refrigeration circuit (compressor(e.g., 120 or 320), the secondary direct-expansion refrigeration circuit(e.g., 125 or 325), or both (e.g., in act 1210, 1220, 1230, 1330, or acombination thereof).

In some embodiments, the method or act (e.g., 1210, 1270, or 1330) ofoperating the secondary compressor (e.g., 120 or 320) includes ensuringthat condensation does not occur during low airflow conditions on thereturn air (e.g., 345 or 1145) or exhaust airstream (e.g., 315 or 1115)side, for example, on the partition (e.g., 111 or 311) described above,for instance, resulting from pressurization needs or variable volumeoperation. Certain embodiments include, for example, increasing thetemperature entering or leaving (or both) the return air (e.g., 345 or1145) side of the dehumidification wheel (e.g., 130 or 330), forinstance, to avoid condensation, for example, during low airflowconditions, for instance, on the return air (e.g., 345 or 1145) side,for instance, on the partition (e.g., 111 or 311), for example,resulting from pressurization needs or variable volume operation.

Further still, in some embodiments, the method or act (e.g., 1210 or1330 of operating the secondary compressor (e.g., 120 or 320) or thesecondary direct-expansion refrigeration circuit (e.g., 125 or 325)includes providing cooling when the chilled water plant or chiller isturned off, for example, due to temperature lockout or time of year, asexamples. Even further, certain embodiments include, for example,operating the system (e.g., 100 or 300) in a part-load mode in whichcooling at the primary cooling coil (e.g., 150, 350, or 1150) is turnedoff and the supply airstream (e.g., 335 or 1135) is cooled using thesecondary cooling coil (e.g., 160 or 360). Particular embodimentsspecifically include (e.g., in act 1210 or 1330) modulating cooling atthe secondary cooling coil (e.g., 160 or 360), for example, to controltemperature of the supply airstream (e.g., 335 or 1135), the space, orboth.

Some embodiments include (e.g., when warranted by conditions)dehumidifying (e.g., in act 1270) the supply airstream (e.g., 335 or1135), for example, with the secondary cooling coil (e.g., 160 or 360),the (e.g., desiccant-based or passive) dehumidification wheel (e.g., 130or 330, for instance, in act 1240 or 1350), or both (e.g., in additionto or instead of cooling with the secondary cooling coil (e.g., 160 or360), for example, when the primary cooling coil (e.g., 150, 350, or1150, for example, operated in act 1250 or 1320) is turned off. Further,in certain embodiments, the method or act (e.g., 1240, 1270, 1350, 1360,or a combination thereof) includes slowing or stopping thedehumidification wheel (e.g., 130 or 330), for instance, when warrantedby conditions, for example, to reduce or avoid reheating the supplyairstream (e.g., 335 or 1135) after being cooled by the secondarycooling coil (e.g., 160 or 360), for example, when the primary coolingcoil (e.g., 150, 350, or 1150) is turned off). Further still, inparticular embodiments, the method or act (e.g., 1210 or 1330) ofoperating the secondary direct-expansion refrigeration circuit (e.g.,125 or 325) or another act, includes reducing the speed of or stoppingthe recovery wheel (e.g., 110 or 310), for example, when warranted byconditions, for instance, to reduce or avoid heating the supplyairstream (e.g., 335 or 1135), for example, prior to being cooled by thesecondary cooling coil (e.g., 160 or 360), for example, when the primarycooling coil (e.g., 150, 350, or 1150) is turned off.

Even further, in some embodiments, the method or act (e.g., 1210 or1330), for example, of operating the secondary compressor or thesecondary direct-expansion refrigeration circuit (e.g., 125 or 325),includes delivering (e.g., in act 1390) colder air than would bepossible with a chilled water system alone, for instance, due to thetemperature limitation of the chilled water available. In particularembodiments, for example, the method or act includes allowing air thatis colder or that has a lower dew point (or both) to be produced anddelivered (e.g., in act 1390), for example, in conjunction with thedehumidification wheel (e.g., 130 or 330), for instance, in comparisonwith a system (e.g., shown in FIGS. 2 and 4) having chilled water thatdoes not have a secondary direct expansion circuit.

Moreover, in some embodiments, the method or act (e.g., 1210 or 1330),for example, of operating the secondary compressor (e.g., 120 or 320) orthe secondary direct-expansion refrigeration circuit (e.g., 125 or 325),includes operating or modulating (or both) the secondarydirect-expansion refrigeration circuit or compressor (e.g., 120 or 320),for example, the system controller (e.g., 170), to deliver (e.g., in act1390) a warmer supply air (e.g., 337) temperature to the occupied spaceor active chilled beams, for instance, to avoid over-cooling of thespace (e.g., in act 1250 or 1320) by the primary airflow alone, forexample, when low dew point is desired (e.g., in act 1270). For example,in some embodiments, the method or act, for example, of operating thesecondary compressor (e.g., 120 or 320) or the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325), includesoperating or modulating (or both) the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) or compressor (e.g., 120 or320), for example, with the system controller (e.g., 170) to increasesupply air (e.g., 337) temperature delivered (e.g., in act 1390) to theoccupied space or active chilled beams, for instance, in response tospace temperature relative to a thermostat temperature setpoint, or inresponse to supply air (e.g., delivered in act 1390) temperature, forexample, to avoid over-cooling of the space by the primary airflow, forinstance, when low dew point is desired.

In some embodiments, the method or act (e.g., 1210 or 1330), forexample, of operating the secondary compressor (e.g., 120 or 320) or thesecondary direct-expansion refrigeration circuit (e.g., 125 or 325),includes providing cooling, dehumidification (e.g., in act 1270), orcondensation control, for instance, during the startup and constructionphase of a building. For example, in certain embodiments, the method oract (e.g., 1210 or 1330) includes operating, controlling, or modulating(e.g., or a combination thereof) the secondary direct-expansionrefrigeration circuit (e.g., 125 or 325) to provide cooling,dehumidification, condensation control, or a combination thereof duringthe startup and construction phase of a building. In some embodiments,due to unconditioned areas, lack of finalized air balancing or controls,the secondary direct-expansion refrigeration circuit (e.g., 125 or 325)can provide temporary cooling (e.g., in act 1210 or 1330), for instance,during times when the space humidity is high or even uncontrollable, atleast to design levels. During these times, for instance, the method oract can prevent condensation, for example, on the dehumidification wheel(e.g., 130 or 330) served by a chilled water system. In varioussituations, this can prevent problems which can damage the wheel orcause corrosion, among other things.

In a number of embodiments, the method or act can include (e.g.,operating or modulating the secondary direct-expansion refrigerationcircuit (e.g., 125 or 325) specifically for (e.g., in act 1210, 1270, or1330) reducing the relative humidity or raising the temperature of thereturn air (e.g., 345 or 1145) or exhaust airstream (e.g., 315 or 1115)before the (e.g., passive) dehumidification wheel (e.g., 130 or 330). Insome embodiments, the method or act can include, for another example,providing temporary cooling, for instance, during times when the spacehumidity is high or even uncontrollable, at least to design levels. Insome embodiments, the method or act can include (e.g., in act 1270), foryet another example, preventing condensation, preventing corrosion,preventing damage, or a combination thereof, for instance, on thedehumidification wheel (e.g., 130 or 330), for example, on systemsserved by a chilled water system.

In various embodiments, the method or act (e.g., 1210 or 1330), forexample, of operating the secondary compressor (e.g., 120 or 320) or thesecondary direct-expansion refrigeration circuit (e.g., 125 or 325),includes modulating down (e.g., reducing in speed or capacity) thesecondary direct-expansion refrigeration circuit (e.g., 125 or 325) orsecondary compressor (e.g., 120 or 320), or even turning off thesecondary direct-expansion refrigeration circuit or secondarycompressor, when conditions within the space have a high sensible loadand a low latent load, when cold air is desired from the system or unit,when condensation on the return air (e.g., 345 or 1145) side leaving the(e.g., passive) dehumidification wheel (e.g., 130 or 330) is not aconcern, or a combination thereof (e.g., all thereof) for example. Undersuch conditions, in some embodiments, the method (e.g., 1200 or 1300)includes cooling (e.g., in act 1210 or 1330) the supply airstream (e.g.,335 or 1135) with the primary cooling coil (e.g., 150, 350, or 1150),for instance. Under such conditions, in certain embodiments, the methodincludes providing dehumidification (e.g., in act 1250, 1270, or 1320)with the primary cooling coil (e.g., 150, 350, or 1150). In someembodiments, for example, the method or act includes turning off thesecondary direct-expansion refrigeration circuit (e.g., 125 or 325) orcompressor (e.g., 120 or 320), for example, that are operated in act1210 or 1330, and providing cooling (e.g., in act 1220, 1250, or 1320)with the primary cooling coil (e.g., 150, 350, or 1150), for example,when conditions within the space have a high sensible load and lowlatent load, when cold air is desired from the unit, when condensationon the return air side (e.g., the exhaust airstream 315 or 1115) leavingthe dehumidification wheel (e.g., 130 or 330) is not a concern, or acombination thereof.

In particular embodiments, the method or act (e.g., 1210 or 1330)includes reducing the speed or capacity of the secondary compressor(e.g., 120 or 320) or reducing the capacity of the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) whenconditions within the space have a high sensible load and low latentload, when cold air is desired from the unit, when condensation on thereturn air side (e.g., the exhaust airstream 315 or 1115) leaving thedehumidification wheel (e.g., 130 or 330) is not a concern, or acombination thereof. In particular embodiments, the method or actincludes implementing these control strategies, for example, underconditions that are relatively hot and dry. In a number of embodiments,the method or act (e.g., 1210, 1270, or 1330) includes modulating downor turning off the secondary direct-expansion refrigeration circuit(e.g., 125 or 325) or compressor (e.g., 120 or 320), for example, inresponse to space temperature relative to one or more thermostatsetpoints and one or more humidity or dew point measurements, forexample.

In some embodiments, the method or act, for example, of operating thesecondary circuit compressor (e.g., 120 or 320) or the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325), includesmaintaining space humidity (e.g., act 1270) for example, duringunoccupied hours, for instance, in a school. In various embodiments, themethod or act (e.g., 1210 or 1330), for example, of operating thesecondary compressor (e.g., 120 or 320) or the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325), includesproviding an unoccupied mode where minimal outdoor air (e.g., 305), andthereby cooling load, is required. In a number of embodiments, themethod or act (e.g., 1210 or 1330), for instance, of operating thesecondary compressor (e.g., 120 or 320) or the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325), includesoperating the secondary direct-expansion refrigeration circuit (e.g.,125 or 325) to perform dehumidification, (e.g., act 1270, for instance,all of the dehumidification needs of the system (e.g., 100, 300, or1100) without operating the primary cooling coil (e.g., 150, 350, or1150), for example, not operating the (or each) chiller or chilledwater, direct expansion (e.g., 1122), or heat pump circuit.

In some embodiments, for example, the method or act includes operatingor modulating the secondary direct-expansion refrigeration circuit(e.g., 125 or 325) or compressor (e.g., 120 or 320) to maintain spacehumidity during unoccupied hours, to provide an unoccupied mode whereminimal outdoor air (e.g., 305), and thereby cooling load, is required,or both. In various embodiments, the method or act (e.g., 1210 or 1330),for example, includes operating or modulating the secondarydirect-expansion refrigeration circuit (e.g., 125 or 325) or compressor(e.g., 120 or 320), for instance, during unoccupied periods, underappropriate conditions, or both, to perform dehumidification (e.g., inact 1270), for example, all of the dehumidification needs, for instance,without operating (e.g., while turning off and leaving turned off) theprimary cooling coil (e.g., 150, 350, or 1150) or the chilled water,direct expansion (e.g., 1122), or heat pump circuit.

Further, various embodiments of the subject matter described hereininclude various combinations of the acts, structure, components, andfeatures described herein, shown in the drawings, described in documentsthat are submitted herewith or incorporated by reference herein, or thatare known in the art. Moreover, certain procedures can include acts suchas manufacturing, obtaining, or providing components that performfunctions described herein or in the documents that are incorporated byreference. The subject matter described herein also includes variousmeans for accomplishing the various functions or acts described herein,in the documents that are submitted herewith or incorporated byreference, or that are apparent from the structure and acts described.Each function described herein is also contemplated as a means foraccomplishing that function, or where appropriate, as a step foraccomplishing that function. Further, as used herein, the word “or”,except where indicated otherwise, does not imply that the alternativeslisted are mutually exclusive. Even further, where alternatives arelisted herein, it should be understood that in some embodiments, feweralternatives may be available, or in particular embodiments, just onealternative may be available, as examples.

What is claimed is:
 1. A system for controlling temperature and humiditywithin a space in a building, the system comprising: a recovery wheel; adesiccant-based dehumidification wheel; a primary cooling coil; and asecondary direct-expansion refrigeration circuit comprising a secondarycircuit compressor, a secondary circuit evaporator coil, and a secondarycircuit condenser coil; wherein: the system forms a supply airstreamthat passes outdoor air first through the recovery wheel, then throughthe primary cooling coil, then through the secondary circuit evaporatorcoil, then through the desiccant-based dehumidification wheel, and thento the space; and the system forms an exhaust airstream that passesreturn air from the space first through the secondary circuit condensercoil, then through the desiccant-based dehumidification wheel, and thenthrough the recovery wheel.
 2. The system of claim 1 wherein: therecovery wheel is a total energy recovery wheel comprising a desiccantcoating; the recovery wheel transfers sensible heat between the outdoorair of the supply airstream and the exhaust airstream; and the recoverywheel transfers moisture between the outdoor air of the supply airstreamand the exhaust airstream.
 3. The system of claim 1 wherein thedesiccant-based dehumidification wheel is a passive dehumidificationwheel and the system further comprises: a supply fan located in thesupply airstream that moves the outdoor air first through the recoverywheel, then through the primary cooling coil, then through the secondarycircuit evaporator coil, then through the desiccant-baseddehumidification wheel, and then to the space; and an exhaust fanlocated in the exhaust airstream that moves the return air from thespace first through the secondary circuit condenser coil, then throughthe desiccant-based dehumidification wheel, and then through therecovery wheel.
 4. The system of claim 1 further comprising a partitionbetween the supply airstream and the exhaust airstream, wherein: therecovery wheel is located in a first opening in the partition; thedesiccant-based dehumidification wheel is located in a second opening inthe partition; at least adjacent to the partition, the supply airstreamand the exhaust airstream travel in substantially parallel directions;at least adjacent to the partition, the supply airstream and the exhaustairstream travel in substantially opposite directions; and the systemfurther comprises an enclosure that contains the recovery wheel, thedesiccant-based dehumidification wheel, the primary cooling coil, thesecondary circuit evaporator coil, the secondary circuit condenser coil,at least part of the supply airstream, at least part of the exhaustairstream, and the partition.
 5. The system of claim 1 furthercomprising a primary direct-expansion refrigeration circuit comprisingthe primary cooling coil as a primary evaporator wherein the primarydirect-expansion refrigeration circuit is a heat pump that both coolsand heats the primary cooling coil depending on whether cooling orheating of the space is demanded.
 6. The system of claim 1 furthercomprising a primary direct-expansion refrigeration circuit comprising:the primary cooling coil which acts as a primary evaporator whenoperating in a cooling mode; a primary condensing coil which acts as acondenser when operating in the cooling mode; and at least one primarycompressor; wherein the exhaust airstream passes through the primarycondensing coil.
 7. The system of claim 6 wherein the return air of theexhaust airstream passes first through the secondary circuit condensercoil, then through the desiccant-based dehumidification wheel, thenthrough the recovery wheel, and then through the primary condensingcoil.
 8. The system of claim 1 further comprising a system controllerconfigured to: operate the secondary circuit compressor whenever thesystem is operating in a cooling mode; operate the secondary circuitcompressor whenever the system is operating in a dehumidification mode;modulate cooling at the primary cooling coil to control temperature ofthe space when operating in the cooling mode; modulate cooling at theprimary cooling coil to control absolute humidity level or dew point ofthe space when operating in the dehumidification mode; modulate coolingat the primary cooling coil to control temperature of the supplyairstream delivered to the space when operating in the cooling mode; andmodulate cooling at the primary cooling coil to control absolutehumidity level or dew point of the supply airstream delivered to thespace when operating in the dehumidification mode.
 9. The system ofclaim 1 further comprising a system controller configured to modulatethe secondary circuit compressor to adjust reheat capacity at thesecondary condenser coil when operating in a cooling mode.
 10. Thesystem of claim 1 further comprising a system controller configured tomodulate rotational speed of the dehumidification wheel based on ameasured temperature of the supply airstream delivered to the space tocontrol the temperature of the supply airstream delivered to the space.11. The system of claim 1 further comprising a system controllerconfigured to operate the system in an economizer mode in which coolingat the primary cooling coil is turned off and the secondary circuitcompressor is operated to dehumidify the supply airstream with thesecondary circuit evaporator coil and the desiccant-baseddehumidification wheel.
 12. The system of claim 1 further comprising asystem controller configured to operate the system in a part-load orrecirculation mode in which cooling at the primary cooling coil ismodulated down or off and cooling at the secondary cooling coil ismodulated to dehumidify the supply airstream using the desiccant-baseddehumidification wheel.
 13. A method for controlling temperature andhumidity within a space in a building, the method comprisingsimultaneous acts of: operating a secondary circuit compressor of asecondary direct-expansion refrigeration circuit that includes thesecondary circuit compressor, a secondary circuit evaporator coil, and asecondary circuit condenser coil; passing outdoor air first through arecovery wheel, then through a primary cooling coil, then through thesecondary circuit evaporator coil, then through a passivedehumidification wheel, and then to the space; and passing return airfrom the space first through the secondary circuit condenser coil, thenthrough the passive dehumidification wheel, and then through therecovery wheel.
 14. The method of claim 13 further comprisingtransferring moisture between the outdoor air and the return air with adesiccant coating on the recovery wheel.
 15. The method of claim 13further comprising modulating the secondary circuit compressor to adjustreheat capacity at the secondary condenser coil when operating in adehumidification mode.
 16. The method of claim 13 further comprising:condensing moisture out of the outdoor air with the secondary circuitevaporator coil; and transferring sensible heat to the return air withthe secondary circuit condenser coil.
 17. A method of controllingtemperature and humidity within a space in a building, the methodcomprising simultaneous acts of: transferring a first quantity of heatfrom outdoor air entering a supply airstream to an exhaust airstream;cooling the supply airstream downstream of the transferring of the firstquantity of heat, including condensing a second quantity of moisturefrom the supply airstream; transferring a third quantity of heat fromthe supply airstream to return air entering the exhaust airstream,wherein: the transferring of the third quantity of heat from the supplyairstream takes place in the supply airstream downstream of the coolingof the supply airstream; the transferring of the third quantity of heatfrom the supply airstream includes condensing a fourth quantity ofmoisture from the supply airstream; the transferring of the thirdquantity of heat from the supply airstream to the return air enteringthe exhaust airstream is performed using a secondary direct-expansionrefrigeration circuit comprising a secondary circuit compressor, asecondary circuit evaporator coil located in the supply airstream, and asecondary circuit condenser coil located in the exhaust airstream;transferring a fifth quantity of moisture from the supply airstream tothe exhaust airstream, wherein the transferring of the fifth quantity ofmoisture from the supply airstream to the exhaust airstream takes placein the supply airstream downstream of the transferring of the thirdquantity of heat from the supply airstream to the return air enteringthe exhaust airstream, and wherein the transferring of the fifthquantity of moisture from the supply airstream to the exhaust airstreamtakes place in the exhaust airstream downstream of the transferring ofthe third quantity of heat from the supply airstream to return airentering the exhaust airstream; in conjunction with the transferring ofthe fifth quantity of moisture from the supply airstream to the exhaustairstream, transferring a sixth quantity of sensible heat from theexhaust airstream to the supply airstream, wherein the transferring ofthe sixth quantity of sensible heat from the exhaust airstream to thesupply airstream takes place in the supply airstream downstream of thetransferring of the third quantity of heat from the supply airstream tothe return air entering the exhaust airstream, and wherein thetransferring of the sixth quantity of sensible heat from the exhaustairstream to the supply airstream takes place in the exhaust airstreamdownstream of the transferring of the third quantity of heat from thesupply airstream to the return air entering the exhaust airstream; anddelivering the supply airstream to the space downstream of thetransferring of the sixth quantity of sensible heat from the exhaustairstream to the supply airstream; wherein: the delivering of the supplyairstream to the space takes place in the supply airstream downstream ofthe transferring of the fifth quantity of moisture from the supplyairstream to the exhaust airstream; and the transferring of the firstquantity of heat from the outdoor air entering the supply airstream tothe exhaust airstream takes place in the exhaust airstream downstream ofthe transferring of the fifth quantity of moisture from the supplyairstream to the exhaust airstream.
 18. The method of claim 17 wherein:the first quantity of heat comprises both sensible and latent heat; theact of transferring the first quantity of heat from outdoor air enteringthe supply airstream to the exhaust airstream further comprisestransferring a seventh quantity of moisture from the outdoor airentering the supply airstream to the exhaust airstream; and thetransferring of the seventh quantity of moisture from the outdoor airentering the supply airstream to the exhaust airstream takes place inthe exhaust airstream downstream of the transferring of the fifthquantity of moisture from the supply airstream to the exhaust airstream.19. The method of claim 17 wherein the cooling of the supply airstreamdownstream of the transferring of the first quantity of heat comprisesremoving an eighth quantity of heat from the supply airstream andrejecting the eighth quantity of heat to the exhaust airstreamdownstream of the transferring of the first quantity of heat to theexhaust airstream.